Chem. Res. Toxicol. 1994, 7, 329-335
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Oxidative DNA Base Damage in Renal, Hepatic, and Pulmonary Chromatin of Rats after Intraperitoneal Injection of Cobalt(I1) Acetate Kazimierz S. Kasprzak,*lt Tomasz H. Zastawny,tp§ Susan L. North,+ Charles W. RiggsJ Bhalchandra A. Diwan,l Jerry M. Rice,? and Miral Dizdaroglui Laboratory of Comparative Carcinogenesis, National Cancer Institute, FCRDC, Frederick, Maryland, 21702, Data Management Services, Inc., and Biological Carcinogenesis Development Program, Program Resources, Inc./DynCorp, NCI-FCRDC, Frederick, Maryland 21702, and Chemical Science and Technology Laboratory, National Institute of Standards and Technology, Gaithersburg, Maryland 20899 Received August 30, 1993"
DNA base damage was studied in renal, hepatic, and pulmonary chromatin of male and female F344/NCr rats that had been given either 50 or 100 pmol of Co(I1) acetate/kg body wt in a single ip dose and killed 2 or 10 days later. Control rats received 200 pmol of sodium acetate/kg body wt. Chromatin was isolated from organs and analyzed by gas chromatography/ mass spectrometry with selected ion monitoring. The following 11products derived from purine and pyrimidine bases in DNA were quantified: 5-hydroxy-5-methylhydantoin,5-hydroxyhy5-hydroxycytosine (5-OH-Cyt),thymine glycol, dantoin, 5- (hydroxymethyl)uraci1(6-OHMe-Ura), 5,6-dihydroxycytosine, 4,6-diamino-5-formamido-pyrimidine (FapyAde), 2,6-diamino-4-hydroxy5-formamidopyrimidine (FapyGua),7,S-dihydro-S-oxoadenine, 2-oxoadenine, and 7,s-dihydro8-oxoguanine. The response was organ-specific. Eight of the DNA base products in renal chromatin of Co(1I)-treated rats (mostly 5-OH-Cyt and other pyrimidine products), five in hepatic chromatin (mostly FapyGua and other purine products), and two in pulmonary chromatin (5-OHMe-Ura > FapyAde) were increased by 30% to more than 200% over control levels with increasing Co(I1) dose. T h e renal and hepatic, but not pulmonary, DNA base damage tended to increase with time. No significant differences in response were found between male and female rats. The bases determined were typical products of hydroxyl radical attack on DNA, suggesting a role for this radical in the mechanism(s) of DNA damage caused by Co(I1) in vivo. Some of these bases have been shown previously to be promutagenic. The present results imply involvement of oxidative DNA base damage in Co(I1)-induced genotoxic and carcinogenic effects.
Introduction Cobalt and its derivatives are toxic and carcinogenic. The relevant data have recently been reviewed by the IARC (I), Beyersmann and Hartwig (2), and Leonard and Lauwerys (3).Although the mechanisms underlying cobalt toxicity, including genotoxicity, have not been established, there is growing evidence that oxygen-derived species may be involved (4-8). It has been shown that certain Co(I1) complexes may facilitate formation of free radical species from H2Oz and/or alkyl hydroperoxides which, in turn, are capable of interacting with and damaging other molecules, including proteins and DNA (6-8). Such damage may lead to cell death, mutation, and cancer. In a previous study (61, Co(I1) was found to promote oxidative modification of DNA bases in mammalian chromatin exposed to H202 in vitro. The modified DNA bases were typical products of hydroxyl radical ('OH) attack on DNA. Chelation of Co(I1) with EDTA almost completely inhibited formation of those products, whereas
* Address correspondence to this author at NCI-FCRDC, Building 538, Room 205, Frederick,MD 21702-1201.Tel: 301-846-5738;F A X 301846-5948. + National Cancer Institute. t National Institute of Standards and Technology. 1 On leave from the Department of Clinical Biochemistry, L. Rydygier Medical School, Bydgoezcz, Poland. I Data Management Services, Inc. 1 Program hources, Inc./DynCorp. Abstract publirhed in Advance ACS Abstracts, March 15, 1994.
glutathione and ascorbate had little or no effect (6). As illustrated by these examples and indicated by other published data (4, 5, 9), the ability of Co(I1) and some other transition metals to mediate oxidative DNA base damage depends on the organic ligand. In a tissue metal cations become bound to a wide variety of natural ligand carriers; therefore, it is difficult to predict the final effect of that binding on the metal's ability to mediate oxidative damage in vivo. In addition, the organic ligands influence not only the reduction potential of a metal cation, but also its uptake, distribution, and retention in subcellular components, including the nucleus. To further test the possible involvement of redox reactions in the mechanism(s) of Co(I1) toxicity and carcinogenicity, it was important to confirm in animals the DNA base damage observed previously in vitro with Co(I1) (6)and in vivo with another carcinogenic transition metal, Ni(I1) (10, 11). The aim of the present experiment was to determine whether systemic administration of Co(11) to rats would increase the levels of DNA base derivatives indicative of oxidative DNA damage (6, 10, 11) in the chromatin of three organs, kidney, liver, and lung. Kidney and liver are the major retention sites for parenterally administered soluble Co(II), while the lung retains relatively less Co(I1) (12-16). Kidney, but not liver and lung, is also a sensitive target for systemic Co(I1) toxicity (1, 1n. Comparison of the Co(I1) effect on DNA base damage in those three organs would thus allow
This article not subject to US. Copyright. Published 1994 by the American Chemical Society
330 Chem. Res. Toxicol., Vol. 7, No. 3, 1994
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Table 1. Levels of DNA Base Products in Kidney. Liver. and Lung Chromatin of Control Rats (nmol/mg of DNA f SDP kidney liver lung 2 days 10 daysb DNA base product 2 days 10 daysb 2 days 10 daysb 0.047 f 0.012 5-OH-5-Me-Hyd 0.068 f 0.020 0.396 f 0.159 0.273 f 0.167 0.181 f 0.055 0.209 f 0.081 0.162 f 0.034 0.115 f 0.059 0.497 f 0.093 0.472 f 0.104 0.290 f 0.027 5-OH-Hyd 0.309 f 0.099 0.047 f 0.037 0.008 f 0.007 5-OHMe-Ura 0.003 f 0.004 0.017 f 0.016
