Yeptemher 19tiS
SOTE:,
activity of both acetylcholine and carbachol. The dose-response curves of acetylcholine ( -11) antagonized b) 1 or 2 were identical within experimental error. The ED,, for both 1 and 2 waq 0.07 mg'ml (ea. -I x 10-4 -11). Previous workers have studied a~etylcarbocholine~ and ticetylsilicocholiiiej and have concluded that these two compounds act as indirect, nonnicotinic, cholinergic :igents. Thiq stud) implies that both 1 and 2 have :in affinity for the mu-c:irinic qite hut (10 not powes:.; intriii4c [ictivitj..
at least five times duriiig and at the eiid of the assays of the test compoiirids. The average of the3e valries wa$ takeii as the 100% ctrritraction valiie for 10-7 .IT acetylcholiiie for the particular miiscle. The t,est compokinds were assayed in essentially the Sam? manner. The initial bath volume was 28 ml. T o this was added 1.0 ml of the test, solution followed within about 15 sec by 1.0 ml of the acetylcholine solution (final bath concent,ration, 10-7 I\. ACh). The process was repeated three times and the average of the peii deflections wab taken as the value for that particiilar coiiceritrat,ion of test rompoiiiid. This value was then expressed as a per cent of the c-oittractioii valiie for lo-' J I ACh. At least foiir animal, were iised for each cvmpoiuid. The data that were obtaiiied are siimmarized i n Figiire I . T h e test rompiiiiiids aloiie gave i i o niiisc-le respoiise in the dose i'aiige of 0.30 to 2..i x 10-3 mg nil.
Experimental Section The procediire described hy TiiriierGwas followed for bioassay piirposes. T h e bath tempemtiire was maintained at 3 i i l o , arid ox>-geiiated Tyrode's soliitioii was iised as the perfiiriiig fliiid. IIexamethoiiiiini bromide (10 nig 1.) was added to the Tyrode'- soliitioii t o preveiit gaiiglioiiica respoiise. The filial bath voliime for each rim was 30 ml aiid chemical concentrations were rnlciilsted accordiiigly. The teht rompoiiiids coiild only be dissolved iii Tyrode's soliitioii with ihe aid of ethaiiol. Ilelivery of 1 ml of the test >oliiiiiiii to 20 ml of tiath gave a final concetitratioii of l.6yc ethaiiol. This did i i o t have a sigiiificaiit iiifliieiice oii the miiscle respoiise iiidiic-ed hy 10-' J I aretylcholine, A typiral rtiii was carried oiit i l l the following manlier. The ileiim was disw'ted, then washed with Tyrode's solution. -4pproximately .i cam of the niriwle was attached to a transducer in the miiscle bath (29 nil) aiid allowed to stand iiiitil the spontaiieoii: cwntract.ioiis had siihsided. The transducer was connected to a strip chart recorder. ilcetylcholiiie chloride sollition (1 ml) (final bath roiicaeiitratioii lo-' JI, 1.6% ethanol) was delivered to the bath. The amplitiide of the strip chart recorder was adjiisted b o that the resiiltirig coiitract.ioii gave a i 0 deflectioii. The mwcle was then washed coiitiniioi Tyrode's soliitioii iiiitil the miiscle had relaxed. The wash soliitioii was drained, f fresh Tyrode's rolritioli was added t o the bath, mid the was allowed t u eqiiilibrate. After the pen tleflecatioii was adjiistedl the c.alibratioii was repeated
DOSE RESPONSE CURVE FH3
A CH,FCH,CH,OCNH,
R
CH,
0
1071
Potential Antimalarial Substances. Antimetabolites of Pantothenic Acid' ED^
IRD
F. E L ~ L L G CX R ~ R, L - \ \ D P HLTT, \ ? D L C ~ L I 11. E ~~ERl3EL
Research 1,ahoialorzes. P a i k e . Daiic and Company, Ann .-libor, Michiqan .@lo6 Recezced llarch 2.5. 1968
I n 1943 it was observed that the survival of the erythrocyt'ic stages of Plasmodium l o p h u m e , maintained intracellularly in duck red cell suspensions in citro, was favored by the addition of calcium pantothenate t o the medium.? lloreover, the development of Plasinoclium qallinaceunz in chickens is inhibited by a deficiency in pantothenic acid These observations stimulated a search for antimetabolites that might interfere with the utilization of pantothenic acid by plasmodia. 3 - 7 Among the antipailtothenates that were synthesized and tested earlier,3 - 7 D-( +)-phenylpantothenone (Ib) vias equiactive with quinine against P.galliiraceunz and twice as potent as quinine against P . lophurae in the c h i c l ~ ~ 1In 7 m:m, I b exhibited slight act'ivit>y against blood-induced vivax malaria and was tolerated well in doses of 2 g daily for 4 days.5 The pantoyltnuriiie derivatives T-13 nnd YIb n-ere the CH? ~IOCII,CCHOHCO?;II(CTT,)ili I
CH3 D-(
Ia, R b, R
= =
+)
coori
COC6Ilj
most active compounds synthesized; both were approximately ten times as pot'ent as quinine against P. gallirruceuin in chicks.jSfi More recently it was shown that pantothenic acid has no effect 011 the erythrocytic stages of P. lophume 0 10
0 05
0 01
BATH CONCENTRATION (mg/ml)
Figure 1. (4) (a) .J. Raaister a n d V. P. Whittaker. .\-atwe, 167, GO5 (1951); (11) A . S. Y. Biiram, Brit. .I. Plinrmncol., 25, 4 (1965). ( 5 ) P. T i l . Henderson. E. J. .\riens, B. TT-. J . Ellenbrock, a n d A . .\I. Simonie, .I. i ' l t i t r m . i'liarmacol., 20, 26 (1968). (6) K . A Turner, "Screening Methods in Pharmacology," Academic Press Inc., Ke,v Y'urk, N . Y.,1965, p p 42-M.
(1) This investigation was supported 11y U a n d Development Command Contract D. Contrihution KO.360 to t h e h r m y Research Program on hlalaria. (2) W , Trager. J . E x p . M e r ! . , 77, i l l (1943). (3) S. Brackett, E. Waletaky, and .\I. Baker, J . F u r o ~ i l o l . ,32, 453 (1945). (4) J. F. Mead, 11. 11. Rapport, .I. E. Senear. J . T . AIaynard. and B i d . Chem., 163, 16.5 (1946). selople, ".I Sur\-ey of .Intimalarial Driigs, 19-11-1945," Vol. I , J. T. Edwards, .\nn Arlmr, 5Iich.. 19.16, p p 138-140. (6) R . \Vinterl)ottom, ,J. \V. Clapp, 11.. H . lliller. J . P. English, a n d R . 0 . Roblin, ,Jr., J . A m . Chem. S O C . , 69, 1393 (1947). ( 7 ) R . E. L u t z , 3. JV. \Vilson, 111, h. J . Deinet, G . H. Harnest, T. -i. Martin, and J. A. Freek, J . U r g . Chrm., 12, 96 (1947).
