Amplification of CCl4 toxicity by chlordecone: destruction of rat hepatic microsomal cytochrome P-450 subpopulation.
Previous work has established marked amplification of CCl4 hepatotoxicity by prior exposure to chlordecone (CD). Since CCl4 is toxic by virtue of its bioactivation by the hepatomicrosomal cytochrome P-450 (cyt P-450) system, which is in turn destroyed, our first interest was to determine if cyt P-450 isozymes were selectively destroyed in this interaction. CoCl2 also decreased hepatic P-450 contents, so our other interest was to observe whether CoCl2 selectively decreased or spared CCl4 metabolizing P-450 enzymes. Solubilized hepatic microsomes from variously treated rats were used. The treatment protocol was dietary CD (10 ppm, for 15 d), and CCl4 (100 microliters/kg, ip). The treatments were CD alone, CCl4 alone, CD + CCl4 and with or without CoCl2 (60 mg/kg/d, sc for 2 d) treatment on d 13 and 14 of the dietary protocol. The control group received normal diet and corn oil vehicle. The key mixed-function oxidase (MFO) parameters measured were microsomal protein, cyt P-450 content, and aminopyrine demethylase (APD). Decrease of P-450 levels ranged from 2.2-fold (CD + CCl4) to 1.3-fold (CD + CoCl2). APD activity decreased by 48 and 26.6% in CD + CCl4 and CD + CoCl2 treatments, respectively. Using an anion-exchange high-performance liquid chromatography (HPLC) column, solubilized microsomal hemoproteins were resolved into five peaks. The P-450 content associated with each peak was determined. In CD rats there was slight increase in peak heights, whereas peak heights in CCl4 and control treatments were similar. CoCl2 decreased all peaks, the decrease of peak I being maximal. In CD + CCl4 treatment, absence of peaks II and III was noted. Microsomal proteins stained for heme showed decreased staining intensity of hemo-protein bands, particularly band 4 (MW 52,000), which was absent in CD + CCl4 interaction. These findings suggest that (1) CoCl2 does not selectively decrease or spare any P-450 isozymes and (2) CD + CCl4 interaction does destroy specific P-450 isozymes.
Chaudhury
S
S
Department of Pharmacology and Toxicology, University of Mississippi Medical Center, Jackson 39216-4505.
Mehendale
H M
HM
D000818:Animals; D002251:Carbon Tetrachloride / Q000633:toxicity*; D007631:Chlordecone / Q000633:toxicity*; D002851:Chromatography, High Pressure Liquid; D003577:Cytochrome P-450 Enzyme System / Q000032:analysis / Q000378:metabolism*; D004357:Drug Synergism; D008297:Male; D008862:Microsomes, Liver / Q000187:drug effects* / Q000201:enzymology; D006899:Mixed Function Oxygenases / Q000378:metabolism; D009251:NADPH-Ferrihemoprotein Reductase / Q000378:metabolism; D009929:Organ Size / Q000187:drug effects; D051381:Rats; D011919:Rats, Inbred Strains
D003577:Cytochrome P-450 Enzyme System; D002251:Carbon Tetrachloride; D006899:Mixed Function Oxygenases; D009251:NADPH-Ferrihemoprotein Reductase; D007631:Chlordecone