Effect of inhibitors of microsomal enzymes on aflatoxin B1-induced cytotoxicity and inhibition of RNA synthesis in isolated rat hepatocytes.
Previous studies conducted in this laboratory demonstrated that AFB1 activation and deactivation was effectively inhibited by metyrapone and TCPO in isolated hepatocytes. The present study was undertaken to study the toxic effect of AFB1 on hepatocyte and RNA synthesis, and to assess the influence of the inhibitors on AFB1-induced cytotoxicity and AFB1-inhibited RNA synthesis. AFB1 at 50 microM was toxic and inhibited macromolecular synthesis by greater than 70% at 180 min of incubation whereas at lower concentrations of AFB1 (0.05-10 microM) dose-and time-dependent decreases in cell viability, protein and RNA synthesis were observed. Using [3H]-AFB1 (0.1.5 microM), the uptake and covalent binding of the toxin were also dose-and time-dependent. Initial rates of these processes to reach half-maximum was found to be 0.25 microM AFB1. In cells treated with AFB1 (5 microM) and metyrapone (1.0 mM) or SKF-525A (10 microM), the cell viability was similar to the control and [3H]-uridine incorporation was significantly higher than AFB1 treated cells. AFB1 and TCPO (0.5 mM) treated cells exhibited further decreases in cell viability and RNA synthesis. Results suggest that the binding of AFB1 to DNA and impairment of transcriptional activity may lead to cell death.
D016604:Aflatoxin B1; D000348:Aflatoxins / Q000633:toxicity*; D000818:Animals; D002273:Carcinogens / Q000633:toxicity*; D002470:Cell Survival / Q000187:drug effects; D066298:In Vitro Techniques; D007700:Kinetics; D008099:Liver / Q000187:drug effects / Q000473:pathology*; D008297:Male; D008797:Metyrapone / Q000494:pharmacology; D008862:Microsomes, Liver / Q000187:drug effects / Q000201:enzymology; D011335:Proadifen / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains; D014158:Transcription, Genetic / Q000187:drug effects*
D000348:Aflatoxins; D002273:Carcinogens; D016604:Aflatoxin B1; D011335:Proadifen; D008797:Metyrapone