Chem. Res. Toxicol. 1991, 4,496-502
496
tabolite of acetaminophen. Drug. Metab. Dispos. 10,47-50. (19) McGirr, L. G., Subrahmanyam, V. V., Moore, G. A., and 0’Brien, P. J. (1986)Peroxidase catalyzed 3-(glutathion-S-yl)-p,p’biphenol formation. Chem.-Bioi. Interact. 60,85-99. (20) McGirr, L. G., and OBrien, P.J. (1987)Glutathione conjugate formation without N-demethylation during the peroxidase catalyzed N-oxidation of N,”,N,N’-tetramethylbenzidine. Chem.Biol. Interact. 61,61-74.
(21) Gant, T.W.,d‘Arcy Doherty, M., Odowole, D., Sales, K. D., and Cohen, G. M. (1986)Semiquinone anion radicals formed by the reaction of quinones with glutathione or amino acids. FEBS Lett. 201,296-300. (22) Shirvastava, M.,Mishra, K. K., and Sinha, B. P. (1982)Kinetics and mechanism of the oxidation of N-acetyl-L-cysteine by 2,6dichloroindophenol in methanol-water medium. Int. J . Chem. Kinet. 14,451-456.
Structure-Activity Relationships for Intracellular Cadmium Mobilization by N-Alkyi-4-O-(~-~galactopyranosyl)D-glucamine-IV-carbodithioates Mark M. Jones* and Pramod K. Singh Department of Chemistry and Center in Molecular Toxicology, Vanderbilt University, Nashville, Tennessee 37235
Glen R. Gale, Loretta M. Atkins, and Alayne B. Smith Veterans Affairs Medical Center and Department of Pharmacology, Medical University of South Carolina, Charleston, South Carolina 29403 Received November 26, 1990 An examination of a group of dithiocarbamate chelating agents derived from various alkylamines and lactose reveals that the relative potencies in the mobilization of intracellular cadmium from renal and hepatic deposits in mice are highly dependent upon the size and nature of the alkyl groups. For those compounds containing straight-chain alkyl groups, the potency drops off as the number of carbon atoms is increased beyond seven. Branched-chain alkyl groups are more effective in promoting the removal of cadmium than straight-chain alkyl groups with the same number of carbon atoms. The fact that these compounds are effective in the mobilization of intracellular cadmium deposits suggests that the size and shape of the alkyl group are important in the determination of the facility with which the compound can pass through cellular membranes. Straight-chain derivatives with 10 or more carbon atoms were more toxic than those with nine or fewer carbon atoms. Of the new compounds, four (the n-hexyl, n-heptyl, n-octyl, and 2-ethylhexyl derivatives) are more effective than the corresponding benzyl derivative in inducing a reduction of hepatic cadmium levels from animals given cadmium a t least 1 week previously. The results obtained indicate that modest modifications in the groups on the basic dithiocarbamate structure can produce agents of significantly enhanced effectiveness for the removal of cadmium from its hepatic deposits.
I ntroductlon Chronic cadmium intoxication in humans frequently involves nephrotoxicity which results from the accumulation of cadmium in the kidneys beyond a critical concentration ( 1 , 2 ) . In this organ, as in the liver, cadmium is stored to a considerable extent as cadmium metallothionein, a complex in which cadmium is very f d y bound (3). Such cadmium can be removed by the administration of either vicinal dithiols, such as dimercaprol (BAL), or dithiocarbamates (4). When dithiocarbamates are used, cadmium mobilization can be accompanied by a reversal of at least some of the signs of renal damage (4,5). For this reason, dithiocarbamates are a more attractive class of compounds than vicinal dithiols for the development of a suitable chelating agent for the treatment of human cases of chronic cadmium intoxication. The present study presents information on the relative renal, hepatic, and whole-body cadmium mobilizing potencies of a series of newly synthesized alkyl derivatives of 4-O-(@-D-galaCtOpyranosy1)-D-glucamine-N-carbodithioates. We have
* Address correspondence to this author at Box 1583,Station B, Vanderbilt University, Nashville, T N 37235.
previously shown that the corresponding benzyl derivatives provide compounds that are among the most potent agents prepared thus far for the mobilization of cadmium from its aged renal and hepatic deposits (6, 7). In the studies presented here, one of these, sodium N-benzy1-4-0-(@-~galactopyranosy1)-D-glucamine-N-carbodithioate (BLDTC), has been used as a standard against which the performance of the other compounds has been measured. Materlals and Methods a-Lactose monohydrate (1) was purchased from Sigma Chemical Co., St. Louis, MO, and the alkylamines (2a-g) were from Aldrich Chemical Co., Milwaukee, WI. Sodium N-benzyl-4-0(8-D-galactopyranosyl)-Dglucamine-N-car~ithi~te (BLDTC) and sodium N-(4-methoxybenzyl)-~gluca”-carbodi (MeOBGDTC) were prepared as described earlier (6). (The structure of BLDTC is as shown in Figure 1 with R = CBH6CH*, Le., a benzyl group.) Proton NMR spectra were recorded on an IBM 3OO-MHz N M R spectrometer in deuterium oxide (D@) wing sodium 3-(trime~ylsilyl)-1-propanesulfonate (DSS) as an intemal standard. The chemical shifts are reported in parts per million (a). IR spectra were recorded on a Perkin-Elmer 710-B spectrometer; only few strong bands have been denoted %”; others were medium or weak. Melting points were determined by wing a Thomas-Hoover stirred liquid apparatus. Microanalyses were
0893-228x191f 2704-0496$02.60f 0 Q 1991 American Chemical Society
Intracellular Cadmium Mobilization by Dithiocarbamates a-Lactose + R-NH2 1
2a-j
1
(i) H20, N2. Steam bath (ii) MeOH, Raney-Ni. H2,900 psi, 4o'c
OH
H
--ii-H7,_. OH
P
/
OH
R
H
B
bH
OH
H
OH
H
0
H
OH
y-'
/
R
\S-Nb
H Q oHH
l-i
OH
4a-j a. R = (CH,),CH3; n-CSLDTC
b, R = (a95cH3; n-C&DTC e, R = (CH2)6CH,;n-CTLDTC
d, R = (CH2)7 CH3; n-CsLDTC e, R = (CH2)8 CH3; n-CgLDTC
F, R = (CH39CH3; n-C10LDTC g, R = (CH2)1oCH3; n-Ci1 LDTC
h, R = (CH911 CH3; n-Clz LDTC 1, R
C-C& l(cyclohexy1); C-c6LDTc ACH2)3CH3; bf-CELDTC j, R = CHzCH .CzH s
Figure 1. Preparations and structures of compounds examined as cadmium mobilizing agents. performed on a Carlo Erba Strumentazione elemental analyzer, Model 1106. Preparation of N-Alkyllactamines (3s-j). The substituted lactamineawere synthesized from a-lactoee (1) and 1molar exceaa of alkylamine (2a-j) in the presence of water on a steam bath under Nz, and the resulting crude imine was hydrogenated (900 psi) at 40 "C for 8-12 days in the presence of Raney Ni catalyst in methanol, according to a recently reported method (6). The completion of the reaction was monitored by 'H NMR. All the secondary amines, except 3a, 31, and 33, were crystallized successfully by using absolute ethanol or 2-propanol and a small quantity of EbO. Compounds 3a, 31, and 3j were purified by repeated precipitations only. The yields and the physical and spectral data are given below. Low-pressure (5040 psi) hydrogenation of the imines achieved by wing PtOz catalyst (ca. 0.5 g of Pto2/15 g of the crude imine) in methanol at 45 "C for 3-4 days also resulted in similar yields of the seconday amines (3a-j) as was achieved with Raney Ni catalyst.
Chem. Res. Toxicol., Vol. 4, No. 4, 1991 497 (a) N-(n-Pentyl)-l-O-(8-~gala~topyrsnosyl)-~glucamine [3a, R = (CH2)&!H3]. Yield 87.4% (white amorphous solid); mp 100-105 "C; 'H NMR (D,O/DSS) 6 4.44 (d, J = 7.7 Hz, 1 H), 3.99-3.48 (m, 12 H), 2.80-2.76 (2 d, 1 H), 2.60-2.53 (m, 3 H), 1.50-1.40 (m, 2 H), 1.27-1.23 (m, 4 H), 0.82 (t,J = 13.6 Hz, 1 H); IR (Nujol) 3350-3300 s (br), 1350,1320,1250, 1235,1150,1120, 1080-1040 s (br), 945, 890, 860, 790 cm-'. Anal. Calcd for C17H~NOlo.l.3H20 C, 46.74; H, 8.68; N, 3.20. Found C, 47.06, H, 8.30; N, 2.78. (b) N-(n-Hexyl)-4-0- (&Dgalactopyransoyl)-Dglucamine [3b, R = (CH2)&H3]. Yield 59% (white granular cystals); mp 111-114 "C; 'H NMR (D2O/DSS) 6 4.47 (d, J = 7.6 Hz, 1 H), 4.02-3.49 (m, 12 H), 2.82-2.79 (2 d, 1 H), 2.62-2.55 (m, 3 H), 1.55-1.45 (m, 2 H), 1.35-1.25 (m, 6 H), 0.86 (t, J = 12.9 Hz, 3 H); IR (Nujol) 3450-3300 s (br), 1405,1330,1300,1240,1225,1200, 1170, 1135, 1115,1070-1040 s (br), 960,910,885,870,840,795, 740,720 cm-'. Anal. Calcd for ClEH37NOlo-0.5H,0 C, 50.57; H, 8.73; N, 3.27. Found C, 49.46; H, 8.68; N, 3.02. (c) N-(n-Heptyl)-4-O-(~-~galactopyranosyl)-~glucamine [3c, R = (CH,),CH,]. Yield 64.0% (white granular cystals); mp 105-108 "C; 'H NMR (DzO/DSS) 6 4.46 (d, J = 7.5 Hz, 1 H), 4.05-4.01 (m, 1 H), 3.89-3.49 (m, 11 H), 2.88-2.84 (2 d, 1 H), 2.67-2.60 (m, 3 H), 1.49 (m, br, 2 H), 1.28 (m, br, 8 H), 0.84 (t, J = 11.7 Hz, 3 H); IR (Nujol) 3450-3300 s (br), 1400,1350,1330, 1295,1220,1170,1135,1115 5,1070 s, 1035 s, 960,890,870,840 cm-'. Anal. Calcd for C19H39NOlo:C, 51.69; H, 8.90; N, 3.17. Found: C, 51.62; H, 9.02; N, 3.11. (d) N - ( n-Octyl)-4-0-(~-~galactopyranosyl)-~-glucamine [3d, R = (CHz)7CH3]. Yield 47.9% (white granular solid); mp 104-106 "C; 'H NMR (DZO/DSS) 6 4.46 (d, J = 7.4 Hz, 1 H), 4.04-3.99 (m, 1 H), 3.90-3.49 (m, 11 H), 2.84-2.81 (2 d, 1 H), 2.65-2.58 (m, 3 H), 1.49 (m, 2 H), 1.28 (m, br, 10 H),0.85 (t, J = 12.3 Hz, 3 H); IR (Nujol) 3425-3350 s (br), 1405, 1355-1325, 1300,1225,1170, 1135, 1120 8, 1080 s, 1065 8, 1040 9,960,895, 875,835 cm-'. Anal. Calcd for C&41NOlo.0.5Hz0 C, 51.71; H, 9.11; N, 3.02. Found: C, 51.97; H, 8.82; N, 2.87. (e) N-(n-Nonyl)-4-O-(,9-~galactopyranosyl)-~~glucamine [3e, R = (CH2),CH3]. Yield 71.1% (white granular crystals); mp 143-145 "C; 'H NMR (DzO/DSS) 6 4.46 (d, J = 7.6 Hz, 1 H), 4.04-3.99 (m, 1 H), 3.88-3.48 (m, 11 H), 2.85-2.81 (2 d, 1 H), 2.65-2.55 (m, 3 H), 1.48 (m, br, 2 H), 1.26 (m, br, 12 H), 0.83 (t, J = 7.0 Hz, 3 H); IR (Nujol) 3450-3210 s (br), 1325,1220,1170, 1130, 1115 5,1080-1040 s,1020,955,890,870,835 cm-'. Anal. Calcd for CzlH~NOlo-0.5Hz0C, 52.70; H, 9.70; N, 2.93. Found C, 52.86; H, 8.95; N, 2.75. (f) N-( n -Decyl)-4-0 -(~-~-galactopyranosyl)-Dglucamine [3f, R = (CH2)9CH3]. Yield 42.9% (white fine granules); mp 120-126 "C; 'H NMR (DzO/DSS) 6 4.46 (d, J = 7.3 Hz, 1 H), 4.04-3.96 (m, 1 H), 3.88-3.50 (m, 11 H), 2.83-2.79 (2 d, 1 H), 2.65-2.51 (m, 3 H), 1.51 (m, br, 2 H), 1.27 (m, br, 14 H), 0.85 (t, J = 11.7 Hz, 3 H); IR (Nujol) 3470-3300 s (br), 1360,1235,1180, 900,880, 1165,1130 s,lO90-1075 s (br), 1050 ~,1030,1000,9~~0, 840 cm-'. Anal. Calcd for Cz2H~NOlo~0.5Hz0 C, 53.64; H, 9.41; N, 2.84. Found C, 53.75; H, 9.16; N, 2.55. (g) N-(n-Undecyl)-4-O-(B-~-galactopyranosyl)-D-glucamine [3g,R = (CHp)lOCHI].Yield 62.9% (white granular solid); mp 140-143 "C; 'H NMR (D20/DSS) 6 4.48 (d, J = 7.2 Hz, 1H), 4.08-3.55 (m, 12 H), 2.86-2.50 (m, 4 H), 1.52 (m, br, 2 H), 1.40 (m, br, 16 H), 0.87 (t, 3 H); IR (Nujol) 3450-3250 s (br), 1350, 1325,1295,1225,1200,1170,1145,1130,1115s,1090-1060 s (br), 1040 s, 1020,985, 960,940, 915,895, 870, 840, 740 cm-'. Anal. Calcd for C23H47NOlo~0.5H20 C, 54.55; H, 9.62; N, 2.77. Found C, 54.65; H, 9.45; N, 2.65. (h) N-( n-Dodecyl)-4- 0 - (B-D-galactopyranosy1)-D-glucamine [3h, R = (CH2)11CH3]. Yield 40.1% (white globular crystals); mp 175-178 "C; 'H NMR (D20/DSS) 6 4.50 (d, 1H), 4.05-3.51 (m, 12 H), 2.85-2.46 (m, 4 H), 1.50 (m, br, 2 H), 1.36 (m, br, 18 H), 0.86 (t, 3 H); IR (Nujol) 3475-3325 s (br), 1325, 1295,1225, 1210,1195, 1170, 1145, 1130 8, 1110 8,1080-1060 s (br), 1040 s, 960 s,940,915,890,870s, 845,830,740 cm-l. Anal. Calcd for C u H a O l d C, 56.34; H, 9.65; N, 2.74. Found: C, 56.28; H, 9.54; N, 2.73. (i) N-Cyclohexyl-4-0-(8-Dgalactopyranosyl)-Dglucamine (31, R = c-CsHl1). Yield 85.1% (white amorphous powder); mp 90-95 "C (foaming);'H NMR (DzO/DSS) 6 4.47 (d, J = 7.7 Hz, 1 H), 4.03-3.49 (m, 12 H), 2.88-2.84 (2 d, J = 3.1 Hz, 1 H),
Jones et al.
498 Chem. Res. Toxicol., Vol. 4, No. 4, 1991
C, 45.38; H, 7.78; N, 2.30. Found: C, 44.92; H, 7.19; N, 2.06. 2.65-2.61 (2 d, J = 9.2 Hz,1H), 2.55-2.45 (m, 1H),1.89-1.57 (m, (g) S o d i u m N - ( n - U n d e c y l ) - 4 - 0 -(B-D-galacto5 H),1.26-1.06 (m, 5 H); IR (Nujol) 3450-3250 s (br), 1360,1210, pyranosy1)-D-glucamine-N-carbodithioate [4g, R = (C1150,108+1040 s (br), 995,920,890,840,720 cm-'.Anal. Calcd H2)10CH3;n-CllLDTC]. Yield 94.4%; mp 188-190 "C dec; 'H for C18H~NOlo~l.3H20: C, 48.16; H, 8.44; N, 3.12. Found: C, NMR (D20/DSS) 6 4.60 (d, J = 7.6 Hz, 1H), 4.48-4.35 (m, 2 H), 48.10; H, 8.37; N, 2.95. (j) N-(2-Ethylhexyl)-4-0-(~-~galactopyranosy1)-~gluc-4.30-4.17 (m, 1H), 4.03-3.55 (m, 13 H), 1.84-1.66 (m, br, 2 H), 1.29 (m, br, 16 H), 0.88 (t,J = 12.5 Hz, 3 H); IR (Nujol) 3450-3300 amine [3j, R = CH&H(C2H,)(CHz)3CH3]. Yield 81.9% (white s (br), 1405,1305,1240,1155,1120,1080-1040s (br), 965 8,895, amorphous solid); mp 94 OC (foaming); 'H NMR (D,O/DSS) 6 855 cm-'. Anal. Calcd for CUHMNNaO1&.1H20: C, 46.97; H, 4.50 (d, J = 7.8 Hz, 1 H), 4.10-4.03 (m,1 H), 3.93-3.51 (m, 11 7.88; N, 2.28. Found C, 47.09; H, 7.58; N, 2.05. H), 2.85-2.82 (2 d, 1H), 2.67-2.46 (m, 3 H), 1.55-1.46 (m, 2 H), (h) S o d i u m N - ( n - D o d e c y l ) - 4 - 0- ( @ - ~ - g a l a c t o 1.35-1.28 (m, br, 8 H), 0.884.84 (m, 6 H); IR (Nujol) 3450-3300 pyranosy1)-D-glucamine-N-carbodithioate[4h, R = (Cs (br), 1350,1340,1310,1245,1210,1140,1115s,108+1050 s (br), Hz)11CH3;n-C12LDTC]. Yield 85.9%; mp 185-189 OC dec; 'H 1030 a, 980, 915, 890, 850, 780 cm-'. Anal. Calcd for NMR (D20/DSS)6 4.62 (d, J = 7.0 Hz,1HI, 4.50-4.35 (m, 2 H), C&,,NOlo~lH20: C, 50.72; H, 9.15; N, 2.96. Found C, 50.76; 4.33-4.18 (m, 1H), 4.05-3.60 (m, 13 H), 1.85-1.66 (m, 2 H), 1.31 H, 8.69; N, 2.71. (m, br, 18 H), 0.89 (t, 3 H); IR (Nujol) 3475-3300 s (br), 1405, Preparation of N-Alkyllactamine Dithiocarbamates 1305,1250,1235,1165,1155,1125s,1080-1050 s (br), 965 8, 890, (4a-j), These dithiocarbamates were prepared from the corre865 cm-'. Anal. Calcd for CzsHleNNaO1&2.5Hz0: C, 45.86; sponding parent amines (3a-j) and an equimolar quantity of H, 8.16; N, 2.14. Found C, 45.71; H, 7.53; N, 1.85. NaOH with an ex- of carbon disulfide in methanol as previously (i) Sodium N-Cyclohexyl-4-0-(B-D-galactopyranosyl)-D reported (6). The products were isolated as white amorphous glucamine-N-carbodithioate[4i, R = c-C&; c-C6LDTC]. solids and were stored refrigerated under Np The yields and Yield 81.0%, mp 150-160 "C (foaming and then decomposition); characterizations are described below. (a) Sodium N-(n-Pentyl)-4-0-(~-Dg~actopyranosyl)-D- 'H NMR (D20/DSS) 6 5.55-5.48 (m, 1 H), 4.52 (d, J = 7.7 Hz, 1H), 4.31-4.02 (m, 2 H), 4.00-3.47 (m,12 H), 1.80-1.73 (m, 4 H), glucamineN-carbodithioate[4a,R = (CH2),CH,; n-C&DTCl. 1.68-1.59 (m, 1 H), 1.47-1.29 (m, 4 H), 1.61-1.08 (m, 1 H); IR Yield 84.8%; mp 150-155 OC (foaming and decomposition), 'H (Nujol) 3300-3200 s (br), 1370,1320,1260,1240,1160,1145,1115, NMR (D,O/DSS) 6 4.56 (d, J = 7.7 Hz,1H), 4.47-4.33 (m, 2 H), 1075-1040 s (br), 960, 915, 895, 720 cm-'. Anal. Calcd for 4.21-4.14 (m, 1 H), 4.01-3.51 (m, 13 H), 1.73-1.67 (m, 2 H), Cl&IMNNaOl,&0.25H20: C, 43.21; H, 6.58; N, 2.65. Found C, 1.36-1.26 (m, 4 H), 0.87 (t,J = 13.8 Hz,3 H); IR (Nujol) 3400-3225 43.51; H, 6.90; N, 2.24. s (br), 1400,1310,1250,1205,1175,1120,1070-1045 s (br), 960, (j) Sodium N-(2-Ethylhexyl)-4- 0 -(B-D-galacto895,860,765,720cm-'. Anal. Calcd for Cl&@"NO1&1.5H2O pyranosyl)-Dglucamine-N-carbit~oate[4j, R = CH2CHC, 40.14; H, 6.91; N, 2.60. Found: C, 40.21; H, 6.62; N, 2.02. (C2€15)(CH2)3CH3;br-C8LDTC]. Yield 90.3%; mp 120-125 "C (b) Sodium N - ( n-Hexyl)-4- 0-(B-D-galactopyranosyl)-D(foaming and then decomposition); 'H NMR (DZO/DSS) 6 4.58 glucamineN-carbodithioate[4b, R = (CH2)&H3;nC&DTC]. (d, J = 7.6 Hz, 1 H), 4.50-4.36 (m, 2 H), 4.33-4.22 (m, 1 H), Yield 88.1%; mp 140-145 OC (foaming and decomposition); 'H 4.06-3.53 (m, 13 H), 2.14-2.03 (m, 1 H), 1.36-1.30 (m, 8 H), NMR (D,O/DSS) 6 4.55 (d, J = 7.7 Hz,1H), 4.42-4.32 (m, 2 H), 0.90-0.86 (m, 6 H); IR (Nujol) 3400-3250 s (br), 1355,1300,1260, 4.21-4.14 (m, 1 H), 4.01-3.51 (m, 12 H), 1.75-1.68 (m, 2 H), 1200,1170,1110,1075-1050 s (br), 1040 8,1020,965 a, 920,890 1.30-1.27 (m, br, 6 H), 0.84 (t, J = 13.2 Hz, 3 H); IR (Nujol) cm-'. Anal. Calcd for CztH,dUNaOt&.lH2O C, 44.12; H, 7.41; 3400-3200 s (br), 1405, 1305, 1275, 1250, 1200, 1170, 1125, N, 2.45. Found: C, 44.05; H, 7.20; N, 2.50. 1080-1040 s (br), 965, 890, 860, 720 cm-'. Anal. Calcd for Animal Studies. Reactor-produced Cd-109 as 'OgCdClzwas CleHssNNa01&2.1.5H20: C, 41.22; H, 7.10; N, 2.53. Found: C, obtained from Du Pont NEN Products, North Billerica, MA. The 41.54; H, 6.79; N, 1.75. (c) Sodium N - ( a-Heptyl)-4-0-(B-~galactopyranosyl)-~ specific activity was 2.22 mCi/mg (82.1 kBq/mg), and the radiochemical purity was >99%. Male mice of the (C57BL/6 X glucamlneNwbodithionte [4c,R = (CH2)&H3; n€.,LDTC]. DBA/2)F1hybrid strain were purchased from the NCI-Frederick Yield 91.9%; mp 140-145 OC (foaming);'H NMR (DzO/DSS) 6 Cancer Research Facility, Frederick, MD, the weights ranged from 4.57 (d, J = 7.5 Hz, 1H), 4.43-4.33 (m, 2 H), 4.26-4.12 (m, 1H), 21 to 24 g upon receipt. After a l-week acclimation period in a 4.00-3.52 (m, 13 H), 1.80-1.61 (m, 2 H), 1.29 (m, br, 8 H), 0.85 facility which was fully accreditad by the AAALAC, each mouse (t, J = 11.9 Hz, 3 H); IR (Nujol) 3400-3200 s (br), 1400, 1350, was given an ip injection of 0.03 mg of CdC12.2.5Hz0 in 1.0 mL 1300,1260,1235,1190,1150,1115,1080-10358 (br), 960,920,890 of 0.9% NaCl solution containing 1.0 pCi (37 kBq) of Cd-109. Mice cm-'. Anal. Calcd for C&&NaOl&32.1.5H20 C, 42.39 H, 7.29; were then returned to the holding facility for at least 1week prior N, 2.47. Found: C, 42.14; H, 7.20; N, 2.29. (d) Sodium N - ( n-Octyl)-4-0-(B-~galactopyranosyl)-~- to the initiation of any treatment regimen. Earlier studies have shown that susceptibility of metallothionein-bound cadmium to glucamineN-carbodithioata[4d,R = (CH2)+2H3;nC&DTC]. dithiocarbamate mobilization is virtually independent of the Yield 83.1%; mp 180-185 OC dec; 'H NMR (D,O/DSS) ii 4.56 (d, elapsed time after cadmium injection within the period of 7-60 J 7.8 Hz,1H), 4.43-4.32 (m, 2 H), 4.24-4.14 (m, 1H), 4.00-3.52 days (refs 8 and 9 and unpublished observations). (m, 13 H), 1.76-1.65 (m, 2 H), 1.30-1.26 (m, br, 10 H), 0.84 (t, When treatment was begun, each compound was given ip in J = 12.8 Hz, 3 H); IR (Nujol) 3400-3250 s (br), 1400,1350,1300, 0.9% NaCl solution, 1.0 mL/30 g mouse, on a daily basis for 5 1260,1230,1190,1160,1120,1075s (br), 1035 8,960,890,775cm-'. days. Three days after the fifth injection, the total retained Anal. Calcd for CZlH,&JNaO1,,S~2H2O C, 42.77; H, 7.52; N, 2.38. cadmium was measured with a rodent whole body y counter (8); Found: C, 42.90; H, 7.16; N, 2.22. phantoms containing Cd-109 which were prepared on the same (e) Sodium N - ( n-Nonyl)-4-~-(~-~galactopyranosy1)-~day that the mice received cadmium permitted calculations of glucamine-N-carbodithioate[k,R = (CH2)&!H3; n-C&IYIVl. the percentage of the administered cadmium which was retained. Yield 85.0%; mp 182-185 OC dec; 'H NMR (DzO/DSS) 6 4.58 (d, Immediately afterward, mice were anesthetized with methoxyJ = 7.6 Hz, 1H), 4.43-4.32 (m, 2 H), 4.25-4.16 (m, 1H), 4.02-3.54 fluorane and decapitated, and selected organs were removed for (m, 13 HI, 1.73 (m, br, 2 HI, 1.28 (m, br, 12 HI, 0.86 (t, br, J = detsrmination of radioactivity with a Beckman Biogamma I crystal 12.9 Hz, 3 H); IR (Nujol) 3400-3300 s (br), 1400,1350,1300,1245, well counter. Results were expressed as pg of cadmium/g of tiesue 1220,1180,1150,1120 8,1090-1050 s (br), 1040 8,960,890,850, wet weight by reference to appropriate standards. 780 cm-'. Anal. Calcd for CnH42NNaOl&z.1.3Hz0: C, 44.70; Data were initially subjected to an analysis of variance. This H, 7.61; N, 2.37. Found: C, 44.76; H, 7.53; N, 1.99. (f) Sodium N - ( n-Decyl)-4-0-(B-~galactopyranosyl)-~- was then followed by application of Duncan's new multiple-range test, with 0.05 set as the acceptable level of statistical significance glucamine-N-carbodithioate[4f, R = (CHZ),CH3; n of differences between means. Cl&DTC]. Yield 87.4%; mp 185-190 OC dec; 'H NMR (DzO/ DSS) 6 4.58 (d, J = 7.6 Hz, 1 H), 4.44-4.31 (m, 2 H), 4.23-4.12 (m, 1H), 4.02-3.54 (m, 13 HI, 1.80-1.65 (m, br, 2 HI, 1.28 (m, br, Results 14 H),0.86 (t, J = 13.3 Hz, 3 H);IR (Nujol) 3410-3300 s (br), All the alkyllactamine dithiocarbamates (4a-j) were 1400,1355,1305,1245,1210,1150,1120,1090-1050 s (br), 1040 obtained in high yields as white amorphous solids and 8,960 8, 890,850 cm-'. Anal. Calcd for CzsH,JV"NO1&1.5H20:
-
Intracellular Cadmium Mobilization by Dithiocarbamates Table I. Cadmium Mobilidng Potency of C6and C, hrivativera whole-body liver, pg of kidney, pg of Cdf g of Cd ae % group administered Cd/g of tissue tissue 4.41 f 0.47 4.61 f 0.40 control 75.06 f 3.83 2.10 f 0.46 2.57 f 0.40 MeOBCDTC 47.38 f 5.60 BLDTC 29.01 i 4.72 2.06 f 0.37 0.86 f 0.34 3.48 f 0.24 1.14 h 0.50 n-C&DTC 35.25 f 6.80 n-C&DTC 27.83 f 2.46 3.51 f 0.25 0.47 f 0.03 3.85 f 0.18 2.99 f 0.31 C-CGDTC 54.86 f 5.28 whole-body levelsf kidney levelsf liver levelsb MeOBGnnDTC BLDTC CLDTC CGDTC C-CaLDTC control */*/* */Sf* *pp *PI* *I*/* MeOBC*J-f* 8f*f* *PI* *I*I DTC BLDTC n-C&DTC n-C&DTC EEachgroup contained 8 mice and received 0.03 mg of CdC12.2.5HZ0 in 1.0 mL of 0.9% NaCl solution containing 1.0 pCi of lOeCdCl1. Two months later each group of mice received the appropriate compound (0.40mmolf kg) in 0.9% NaCl solution, 1.0 mL ipf 30 g of m o w weight on each of 5 successive days. Whole-body cadmium levels were measured 3 days later, and the mice were then sacrificed and the kidneys and livers removed for cadmium determination with a crystal well counter. Data are means fl.O SD. bThe levels of significance of the differencea between the group were determined by wing Duncan's new multiple-range test and are shown in the lower part of the table: (*) indicates p I0.05; (-1 indicates that the difference is not significant.
melted with decomposition. They were stable at ambient temperature under N2or Ar for a t least a month. The parent secondary amines (3a-j) with the exception of n-pentyl- (3a), cyclohexyl- (3i), and (2-ethylhexy1)lactamine (3j) could be crystallized as granular crystals. The preparation routes and structures are summarized in Figure 1. Because of the large number of compounds used, it was necessary to run the comparisons in two groups, each of which contained a control (untreated) group and a group which was administered BLDTC as a standard treatment. The results obtained are presented in Tables I and 11.
Chem. Res. Toxicol., Vol. 4, No. 4, 1991 499 Table I contains data on C6 and Ce alkyl compounds in addition to comparable data on MeOBGDTC. Table I1 contains the results for the C,-CI2 alkyl compounds. The data presented in Table I indicate that the n-hexyl derivative, n-C&DTC (4b),is superior to BLDTC in reducing hepatic cadmium burdens. The unexpectedly low effectiveness of the cyclohexyl derivative is also noteworthy, as well as the observation that the compounds containing a benzyl group are superior in effecting a reduction of renal cadmium levels to those compounds devoid of this structure. Brain cadmium levels subsequent to the administration of MeOBLDTC and BLDTC have previously been shown to undergo no significant change (6). The data on the longer chain alkyl derivatives in Table I1 also show some interesting features. First, the activity in reducing whole body and hepatic cadmium levels changes only slightly from C, to C9 in straight-chain series. The fact that the derivatives from Clo to CI2 are much more toxic (mortality was the only index of toxicity used here) indicates clearly that these compounds are less suitable than those with a shorter alkyl chain. 'The only branched-chain group is present in br-C8LDTC (4j), and this analogue was more active than its straight-chain isomer, n-C&DTC (4d), in effecting the reduction of renal cadmium levels. These results clearly show that the most active compounds (of those shown in Table 11) for the reduction of the hepatic cadmium levels are the C,-Co compounds, n-C7LDTC, n-C8LDTC, br-C8LDTC, and n-CgLDTC, while the compound that is the most effective for the reduction of the renal cadmium levels is the branched chain c8 derivative, br-C,LDTC. Th.e results obtained with the longer chain alkyl groups and with branched-chain groups are consistent with common observations found for other types of drugs (13). A comparison of the data in the tables shows that a compound such as BLDTC loses none of its cadmium mobilizing activity as the time interval increases between cadmium loading and the initiation of chelate treatment. In Table I, after treatment with BLDTC, 2-month-old cadmium deposits were reduced by essentially the same extent as those deposits that were 2 weeks old (Table 11):
Table 11. Whole-Body, Kidney, Liver, and Brain Cadmium Levels after Alkyllactamine Dithiocarbamate Treatment" whole-body Cd kidney, Yg of liver, fig of brain, pg of group ae % administered CdJg of tissue CdJg of tissue Cd/g of tissue contrL. 89.42 f 2.39 3.55 f 0.20 6.13 0.39 0.026 f 0.004 BLDTC 35.84 f 7.06 1.76 f 0.24 1.32 f 0.58 0.028 f 0.004 n-C,LDTC 29.77 f 0.76 2.94 f 0.25 0.543 f 0.066 0.026 f 0.003 n-C8LDTC 32.34 f 4.20 3.40 f 0.14 0.644 i 0.274 0.023 f 0.004 n-C&DTC 36.14 f 5.02 3.40 f 0.18 1.15 f 0.50 0.027 0.002 n-Cl&DTC 80.25 f 11.82 3.42 f 0.032 5.18 i 1.09 0.027 f 0.007 n-Cl1LDTC 85.67 f 12.18 3.66 f 0.48 5.77 f 0.72 0.027 f 0.007 n-C12LDTC 86.32 f 2.39 3.77 f 0.36 6.38 i 0.65 0.029 f 0.004 br-C8LDTC 30.24 f 3.67 2.10 f 0.23 0.563 f 0.146 0.025 f 0.005 whole-body cadmium levelsf kidney cadmium levelsf liver cadmium levelsb BLDTC n-C,LDTC n-C8LDTC n-C&DTC n-Cl&DTC n-CllLDTC n-ClzLDTC br-C8LDTC
-1-1-1-l*PI* control *PI* ' 1 '1* *I-P *I-I* *I-I* *I *1* *I*/* -PI* BLDTC -PI * -PI* -1.1*I*/* n-C,LDTC -PI-PI*/*I* */*I* *PI* -PIn-C&DTC -1-l*I-I* *I-I* */*/* -PI* * * *I *In-C&DTC *l-l* *I-P I1 I * * n-Cl&DTC -1-l-l*l* I1 ** I** */ * n-Cl1LDTC -I -I n-C12LDTC I1 "Each group contained six or seven male BDFl mice. Each mouse was given 0.03 mg of CdClZ-2.5Hz0in 1.0 mL of 0.9% NaCl which contained 1.0 pCi of WdCIp One week later each animal was started on a series of injections of the appropriate chelating agent at 0.40 mmolf kg given ip, once a day for 5 days, except for n-Cl&DTC, n-CllLDTC, and n-CIZLDTC,which were given only once because of their toxicity at this level. Three days after the end of this period, the whole-body content of cadmium were determined and the animal were then sacrificed, and kidneys, livers, and brains were removed for determination of cadmium levels. bThe levels of significance of the differences between groups were determined by uing Duncan's new multiple-range test and are shown in the lower part of the table: (*) indicates that p I0.05; (-1 indicates that the difference is not significant. None of the differences in the brain cadmium levels are significant.
500 Chem. Res. Toxicol., Vol. 4,No.4,1991
Jones et al.
Table 111. Dose-Response Relationships for Cadmium Mobilization by BLDTC and n -C6LDTCa whole-body Cd group as % administered kidney Cd, pg/g liver Cd, pg/g
control 92.50 f 4.87 3.79 f 0.32 5.47 f 0.27 BLDTC (0.25 mmolfkg) 41.64 5.75 2.00 f 0.15 1.31 i 0.36 BLDTC (0.50 mmolfkg) 31.12 i 1.94 1.55 f 0.09 0.58 f 0.09 BLDTC (1.00 mmolfkg) 27.43 0.66 1.05 f 0.19 0.44 i 0.03 n-C&DTC (0.25 mmolfkg) 38.43 f 3.61 2.86 f 0.25 1.04 f 0.18 n-C&DTC (0.50 mmolfkg) 31.37 f 1.07 2.86 f 0.23 0.52 i 0.08 n-C6LDTC (1.00 mmolfkg) 29.87 i 1.19 2.57 f 0.44 0.44 f 0.04 BLDTC (0.50 mmolfkg) + n-C&DTC (0.50 mmolfkg) 26.75 f 2.12 1.34 f 0.16 0.39 i 0.05 whole-bodv Cd valuedkidnev Cd values/liver Cd valuesb BLDTC BLDTC BLDTC BLDTC +(0.25 (0.50 (1.00 n-CsLDTC n-CsLDTC n-CeLDTC &LDTC mmol/ka) mmol/ka) mmol/ka) (0.25 mmol/kd (0.50 mmol/kd (1.00 mmol/ke) (0.50 mmollke each)
* *
~~
~~~
control */*I* */*I* */*I* *I*/* */*I* *I*/* */*I* BLDTC (0.25 mmolfkg) */*I* */*I* -/*I* */*I* */*I* *I*/* BLDTC (0.50 mmolfkg) -/*I*/*/* -I*/-/*/-/*IBLDTC (1.00 mmolfkg) *I*/* */*/-/*I-/*/n-C&DTC (0.25 mmolfkg) *I-/* */*I* */*I* n-C8LDTC (0.50 mmolfkg) -/*I*/*/n-C&DTC (1.00 mmolfkg) -I*/a Each group contained eight mice and received 0.03 mg of CdCl2.2.5H,O in 1.0 mL of 0.9% NaCl solution containing 1.0 pCi of "WdCl, ip. Eleven days later each group of mice received the compound(s) indicated in 0.9% NaCl solution at the indicated dose levels ip, 1.0 mL/30 g of mouse weight, on each of 5 consecutive days. Three days later, whole-body cadmium burdens were measured, and mice were immediately sacrificed for removal of kidneys and livers and determination of the cadmium concentrations with a crystal well counter. Values given are means f 1.0 SD. bThe levels of sgnificance of the differences between the groups were determined by using Duncan's new multiple-range test and are shown in the lower part of the table: (*) indicates p I 0.05; (-) indicates that the difference is not significant.
whole body, 38.6% vs 40.0%; kidneys, 46.7% vs 49.5%; and liver, 18.7% vs 21.5'31,all in comparison to control values. The data clearly show that compounds which are most active in reducing renal cadmium levels are not the same as those which are most effective in reducing hepatic cadmium levels. Dose-response data were obtained for two of the most effective of the compounds examined here, BLDTC and n-CADTC, as shown in Table 111. It can be seen that the whole-body and liver cadmium data are very similar for these two compounds, though BLDTC is slightly more effective in removing cadmium from the kidney.
Dlscusslon One of the most surprising of the structure-activity relationships observed is the clear demonstration that none of the alkyl derivatives examined was as effective as BLDTC in reducing the renal cadmium levels. The fact that the most effective alkyl derivatives in the mobilization of hepatic cadmium were those with straight-chain alkyl groups (n-C&DTC, n-C7LDTC,and n-C,LDTC) was also unexpected, as previous studies on closely related series of glucamine derivatives indicated that this property was dependent on the molecular weight of the compound (10, 11). There is also a dependence on the value of ET,the sum of the Hansch constants, of the groups involved (IO, 11). The increased potency of the branched chain, as opposed to the isomeric straight chain, is expected, as it is very similar to the changes found with derivatives of glucamine (12). Because little doseresponse information is available for the mobilization of intracellular cadmium, the present results are of interest in indicating the shapes of the dose-response curves for such processes. These data clearly indicate that a dose of 1.0 (mmol/kg)/day for 5 days produces a response on the upper part of the doseresponse curve for the removal of cadmium from liver. At the highest dose of n-C&DTC used, only 7% of the control levels of cadmium is found to remain; for BLDTC only 8% remains. Inasmuch as this dose is not close enough to a
lethal level to cause death in any of the animals, these results suggest that the efficacy (=maximum potency) of these compounds for the removal of cadmium from the liver is 100% or very close to it. The lowest doses used indicate that, even at a level of only 0.25 (mmol/kg)/day, an appreciable fraction of both renal and hepatic cadmium can be removed by the best of these agents. The actual efficacies of most chelating agenta for the removal of toxic metals in cases of chronic intoxication are not known. The reductions of kidney cadmium by these compounds are not so great; at the highest doses used, 28% of the cadmium remains after treatment with BLDTC and 35% remains after treatment with n-CADTC. The whole-body results are analogous to those for the kidneys: 30% of the control cadmium remains after treatment with BLDTC and 29% after n-C6LDTC. The nearly equal effectiveness of these compounds in reducing liver cadmium is consistent with earlier correlations we obtained which indicated that one of the main factors in governing this effectiveness is the molecular weight of the compound (IO),and the molecular weights of these two compounds are quite close (BLDTC = 531.58and n-C&DTC = 525.62). The other factor is the value of ET;the values of this parameter for these two compounds (neglecting that of the charged dithiocarbamate group present in both) also do not differ greatly (BLDTC, ET = -5.81;and n-C&DTC, ET = -4.73). In cases where compounds such as these are compared, however, it must be remembered that the correlations for aliphatic and for aromatic groups are different (10, 11). From the data shown in Tables I and 11, the selection of a single compound as the optimal agent in terms of potency is dependent upon whether the maximum removal of cadmium is desired from the kidney or the liver. The advantage of removing cadmium from the kidney lies in the fact that the initial stages of renal damage found with chronic cadmium intoxication in the rat may be reversed by treatment with dithiocarbamates such as those described here (14,15).The advantage of using a compound that removes the maximum amount of cadmium from the liver lies in the fact that this thus removes the reservoir of cadmium in the liver which would otherwise be trans-
Intracellular Cadmium Mobilization by Dithiocarbamates ported to the kidneys upon cessation of treatment. This completely circumvents the previously described processes by which a toxicologically significant fraction of the liver cadmium is transported to the kidney (3,16,17,18).The advantage of a compound such as br-C8LDTC is that it is very effective in removing cadmium from both organs. An examination of the data obtained for relationships between structure and activity reveals some interesting features. As can be seen from the data in Table 11, those compounds with alkyl groups with 10, 11, or 12 carbon atoms were found to be sufficiently more toxic than the other compounds that the condition of the animals precluded the administration of more than the initial injection. For compounds with C5-Cs alkyl groups, only the C8 branched-chain alkyl compound was notably effective in reducing renal cadmium levels. What was quite striking about all of the alkyl derivatives with five to nine carbon atoms was their notable potency in reducing hepatic and whole-body cadmium levels. For the straight-chain compounds in this group (C5-Cs only; the data on the ClO-Cl2 compounds were omitted from the correlations below because the data were not obtained with comparable dosages) for which values could be determined from standard tables (19) for the parts of the molecule other than the ionic dithiocarbamate group, the correlation equation for liver cadmium levels following standard treatment is [ C d t r e dCdoontm~l= 2.071 + 0.974xu + 0.119(c~)~, 9 = 0:963 This indicates an optimum value of C u for the removal of cadmium from the liver at -4.10. The values used for the term X u for these compounds were estimated from standard tables (19) and were as follows: C5, -5.27;C6, -4.73; C,, -4.19; Cg, -3.65; Cg, -3.11. For whole-body cadmium level reductions by the same group of compounds the corresponding correlation equation was found to be [Cdtreatod/Cdeontroll = 1.73 + 0.69cu + (8.55X 10-2)(cs)2, 9 = 0.974 which has an optimum value for whole-body cadmium = -4.04.This is not suprising as a very mobilization of large fraction of the whole body cadmium burden is in the liver. For the depletion of renal cadmium for correlation equation found for the C5-Cs compounds was [Cdtreatod/Cdcontroll = 1.596 + 0.262cu + (2.03 X 10-2)(cu)2, r2 = 0.874 Here the optimal value for c s is expected to be -6.45. Since the fractional reduction of renal levels expected at this value was only 0.75,a value inferior to that of the benzyl compound (BLDTC), as well as the branched-chain C8 derivative (br-C8LDTC), the search for straight-chain akyl compounds more effective for renal cadmium removal was not pursued. In these compounds the molecular weight was nearly constant; therefore, no correlations involving this factor were detected. Correlations of this sort involving terms in x u and in are very common, as can be seen in standard works (19-21). They are generally interpreted as arising from a random walk process involving the transport of the compound. A comparison of the correlations obtained here with those reported earlier (10-12) for cadmium mobilization reveals several points of interest. First, the benzyl group is generally superior to a straighbchain alkyl or cycloalkyl group with a comparable number of carbon atoms in inducing the removal of cadmium from its aged renal de-
Chem. Res. Toxicol., Vol. 4, No. 4, 1991 501 posits, but is inferior to the straight-chain alkyl analogues with an equal or slightly greater number of carbon atoms for the mobilization of aged hepatic deposits. Second, branched-chain analogues in the region C5-C8(where data are available) are invariably superior to their straight-chain analogues for inducing the removal of both renal and hepatic cadmium (Tables I and 11), a finding that was also reported in an earlier study (12). Third, the types of alkyl groups that provide compounds of greatest potency are similar for both glucose and lactose, though this does not hold for aralkyl derivatives such as the benzyl group. The poor showing of longer chain alkyl derivatives (C, and above) is a common feature as is their greater toxicity. Compounds with such long alkyl chains are too toxic for serious consideration in view of the availability of more effective compounds which do not suffer from this disadvantage. The results of these studies suggest that the two most promising substituent types for compounds of this sort are the aralkyl and branched-chain alkyl derivatives with five to eight carbon atoms. The correlations obtained here and in previous examinations of cadmium mobilizing agents (10-12) suggest strongly that compounds of considerably greater potency than those presently available can be obtained by extrapolation of the correlations beyond the sets of compounds examined so far. The results presented here clearly demonstrate that a significant enhancement in the effectiveness for the mobilization of intracellular cadmium may be attained by relatively modest changes in groups which are joined by the basic dithiocarbamate structure. They also show that such cadmium can be mobilized with doses of these compounds as low as 0.25 (mmol/kg)/day.
Acknowledgment. We acknowledge the support of this work by the National Institute of Environmental Health Sciences via Grant ES-02638 (M.M.J.) and by the Department of Veterans Affairs (G.R.G.).
References (1) Goyer, R.A. (1989) Mechanisms of lead and cadmium toxicity. Toxicol. Lett. 46, 153-162. (2) Cherian, M. G., and Goyer, R. A. (1989) Cadmium toxicity. Comments Toxicol. 3, 191-206. (3) Piscator, M. (1986) The Nephrotoxicity of Chronic Cadmium Intoxication. In Cadmium (Foulkes, E. C., Ed.) pp 179-194, Springer Verlag, Berlin. (4) Jones, M.M., and Cherian, M. G.(1990) The search for chelate antagonists for chronic cadmium intoxication. Toxicology 62, 1-25. (5) Kojima, S.,Ono, H., Kiyozumi, M., Honda, T., and Takadate, A. (1989) Effect of N-benzyl-D-glucaminedithiocarbamate on the renal toxicity produced by subacute exposure to cadmium in rats. Toxicol. Appl. Pharmacol. 98, 39-48. (6) Jones, M. M., Singh, P. K., and Jones, S. G. (1990) Optimization of chelating agent structure for the mobilization of aged renal and hepatic cadmium doposits: Sodium N-benzyl-4-0-(8-~-galactopyranosy1)-Dglucamine-N-carbodithioate. Chem. Res. Toxicol. 3, 248-253. (7) Jones, M. M., Singh, P. K., Jones, S. G., and Holscher, M. A. (1990) Dithiocarbamates of improved efficacy for the mobilization of aged cadmium from renal and hepatic deposits. Pharmacol. Toxicol. 68, 115-120. (8) Gale, G . R., Atkins, L. M., Walker, E. M., Jr., and Smith, A. B. (1983) Comparative effects of diethyldithiocarbamate, dimercaptosuccinate,and diethylenetriaminepentaacetate on organ distribution and excretion of cadmium. Ann. Clin. Lab. Sci. 13, 33-44. (9) Gale, G. R.,Atkins, L. M., Smith, A. B., Jones, S. G., and Jones, M. M. (1988) Dithiocarbamate treatment of chronic cadmium intoxication in mice. Toxicol. Lett. 44, 77-84. (10) Singh, P.K.,Jones, M. M., Jones, S. G., Gale, G. R., Atkins, L. M., Smith, A. B., and Bulman, R. A. (1989) Effect of chelating agent structure on the mobilization of cadmium from intracellular deposita. J . Toxicol. Enoiron. Health 28, 501-518.
502 Chem. Res. Toxicol., Val. 4, No. 4, 1991 (11) Singh, P. K., Jones, S. G., and Jones, M. M. (1990)Structural
factors in the in vivo chelate mobilization of aged cadmium deposita. Enuiron. Health Perspect. 85, 361-370. (12) Jones, M.M., Singh, P. K., Jones, S. G., Mukundan, C. R., Banton, J. A., Gale, G . R., Atkins, L. M., and Smith, A. B. Chirality, charge, and chain branching effects on dithiocarbamateinduced mobilization of cadmium from intracellular deposits in mice. Chem. Res. Toxicol. 4, 27-34. (13) Burger, A. (1983)A Guide to the Chemical Basis of Drug Design, pp 82-84,John Wiley & Sons, New York. (14) Kojima, S., Ono, H., Kiyozumi, M., Honda, T., and Takadate, A. (1989)Effect of N-benzyl-D-glucamine dithiocarbamate on the renal toxicity produced by subacute exposure to cadmium in rats. Toxicol. Appl. Pharmacol. 98,39-48. (15) Kojima, S.,Ono, H., Furukawa, A., and Kiyozumi, M. (1990) Effect of N-benzyl-D-glucamine dithiocarbamate on renal toxicity induced by cadmium-metallothionein in rats. Arch. Toxicol. 64, 91-96.
Jones et al. (16) Dudley, R. E., Svoboda, D. J., and Klaassen, C. D. (1982)Acute exposure to cadmium causes Bevere liver injury in rata. Toxicol. Appl. Pharmacol. 65, 302-313. (17) Foulkes, E.C. (1990)Transport of heavy metals by the kidney. Toxicol. Lett. 53, 29-31. (18) Nordberg, G. F., KjellstrBm,T., and Nordberg, M. (1985)Kinetics and metabolism. In Cadmium and Health A Toxicological and Epidemiological Appraisal Friberg, L., Elinder, C.-G., KjellstrBm, T., and Nordberg, G. F., Eds.) Vol. 1, pp 103-178, CRC Press, Boca Raton, FL. (19) Hansch, C., and Leo, A. (1979) Substituent Conrrtants for Correlation Analysis in Chemistry and Biology, pp 49-54, John Wiley & Sons, New York. (20)h k e , R. (1984)Theoretical Drug Design Methods, pp 53,165, and 182,Elsevier, Amsterdam. (21) Hansch, C., and Fujita, T. (1964)p-u-ri Analysis. A method for the correlation of biological activity and chemical structure. J. Am. Chem. SOC. 86,1616-1626.
Announcements INTERNATIONAL CONFERENCE ON ENVIRONMENTAL AND BIOLOGICAL ASPECTS OF MAIN-GROUPS ORGANOMETALS
The University of Padua and the Italian Chemical Society are sponsoring an International Conference on Environmental and Biological Aspects of Main-Groups Organometals to be held September 15-19,1991,at the University of Padua, Padova, Italy. The Conference deals with the following typical subject areas: methylation (alkylation) of heavy metals and determination, speciation, and toxicology of alkylated materials; toxicology of organometallics and fate in organisms; release, pathways, and fate of organometallics in the environment; organometallics and chemotherapy, their role as antibacterial and antiviral agents; organometallic tumor targetting chemistry; diffusion studies with organometallics in plastics, foods, etc.; organometallic compounds and agricultural applications; and treatment of industrial waste organometallic compounds. The program will include plenary lectures and contributed papers (oral communications and poster sessions). The Conference languages will be those of the FECS, but use of English is recommended. Participation is limited. For further information, please contact Professor Giuseppe Tagliavini, Chairman, ICEBAMO, c/o DCIMA, Universita di Padova, Via Marzolo 1,I-35131Padova, Italy (telephone, 049-831272;FAX, 049-831249;Telex, 430 UNPADU I).
INTERNATIONAL COMMITTEE ON ALCOHOL, DRUGS AND TRAFFIC SAFETY AND UNITED NATIONS FUND FOR DRUG ABUSE CONTROL: INTERNATIONAL WORKSHOP ON “DRUGS AND DRIVING: METHODOLOGY I N MAN-MACH INE INTERACTION AND EPIDEMIOLOGY STUDIES”
The International Committee on Alcohol, Drugs and Traffic Safety and the United Nations Fund for Drug Abuse Control will be sponsoring an International Workshop on “Drugs and Driving: Methodology in Man-Machine Interaction and Epidemiology Studies”, October 28-November 1,1991, at the University of Padova in Padova, Italy. The Workshop has scientific and operative aspects and is aimed at unifying the international methodology in the following research areas: (1)manmachine interaction; (2)special population surveys; and (3)toxicological assay of psychoactive drugs in biological fluids. The idea is to propose, discuss, and approve a methodology that can be used on an international level to enable a comparison of results between researchers. The definitive methodology that will be developed from the experts’ and participants’ discussion during the Workshop will be published, with the approval of the International Committee on Alcohol, Drugs and Traffic Safety, in a Manual that will be recommended as a working tool to all researchers in this field. Participation is limited. For further information, please contact Professor S. D. Ferrara, Centre of Behavioural and Forensic Toxicology,UNFDAC Collaborating Center, Instituto Medicina Legale, State University, Via Falloppio 50,35121 Padova, Italy (telephone/FAX, 049-875-1087;Telex, 430176 UNPADU).
