FURAN-MEDIATED UNCOUPLING OF HEPATIC OXIDATIVE-PHOSPHORYLATION IN FISCHER-344 RATS - AN EARLY EVENT IN CELL-DEATH

Furan is a potent rodent hepatotoxicant and carcinogen, The present st udy was done to examine the effects of furan on hepatic energy metabol ism both in vivo and in vitro in male F-344 rats, Furan produced conce ntration- and incubation time-dependent irreversible reductions in ATP in freshly isolated F-344 rat hepatocytes, Furan-mediated depletion o f ATP occurred prior to cell death and was prevented by including l-ph enylimidazole, a cytochrome P450 inhibitor, in the suspensions. Male F -344 rats were treated with furan (0-30 mg/kg, po) and killed 24 hr la ter to prepare hepatic mitochondria. Furan produced dose-dependent inc reases in state 4 respiration and ATPase activity. Both of these chang es were prevented by l-phenylimidazole cotreatment. In a separate seri es of experiments, mitochondria were prepared from isolated rat hepato cytes following incubation with furan (2-100 mu M) for 1-4 hr, Furan p roduced incubation time- and concentration-dependent increases in stat e 4 respiration and ATPase activity, Furan-mediated mitochondrial chan ges were prevented by adding I-phenylimidazole to the hepatocyte suspe nsions. These results indicate that the ene-dialdehyde metabolite of f uran uncouples hepatic oxidative phosphorylation in vivo and in vitro, In vitro studies using an isolated hepatocyte suspension/culture syst em demonstrated that the concentration response for furan-mediated mit ochondrial changes in suspension corresponded with the concentration r esponse for cell death after 24 hr. Including l-phenylimidazole or oli gomycin plus fructose in hepatocyte suspensions prevented furan-induce d cell death after 24 hr in culture, The results of this study indicat e that furan-induced uncoupling of oxidative phosphorylation is an ear ly, critical event in cytolethality both in vivo and in vitro. (C) 199 7 Academic Press.