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 study was done to examine the effects of furan on hepatic energy metabolism both in vivo and in vitro in male F-344 rats. Furan produced concentration- and incubation time-dependent irreversible reductions in ATP in freshly isolated F-344 rat hepatocytes. Furan-mediated depletion of ATP occurred prior to cell death and was prevented by including 1-phenylimidazole, a cytochrome P450 inhibitor, in the suspensions. Male F-344 rats were treated with furan (0-30 mg/kg, po) and killed 24 hr later to prepare hepatic mitochondria. Furan produced dose-dependent increases in state 4 respiration and ATPase activity. Both of these changes were prevented by 1-phenylimidazole cotreatment. In a separate series of experiments, mitochondria were prepared from isolated rat hepatocytes following incubation with furan (2-100 microM) for 1-4 hr. Furan produced incubation time- and concentration-dependent increases in state 4 respiration and ATPase activity. Furan-mediated mitochondrial changes were prevented by adding 1-phenylimidazole to the hepatocyte suspensions. These results indicate that the ene-dialdehyde metabolite of furan uncouples hepatic oxidative phosphorylation in vivo and in vitro. In vitro studies using an isolated hepatocyte suspension/culture system demonstrated that the concentration response for furan-mediated mitochondrial changes in suspension corresponded with the concentration responses for cell death after 24 hr. Including 1-phenylimidazole or oligomycin plus fructose in hepatocyte suspensions prevented furan-induced cell death after 24 hr in culture. The results of this study indicate that furan-induced uncoupling of oxidative phosphorylation is an early, critical event in cytolethality both in vivo and in vitro.
Mugford
C A
CA
Chemical Industry Institute of Toxicology, Research Triangle Park, North Carolina 27709-2137, USA.
Carfagna
M A
MA
Kedderis
G L
GL
D000255:Adenosine Triphosphate / Q000378:metabolism; D000818:Animals; D017209:Apoptosis / Q000187:drug effects*; D001711:Biotransformation; D002273:Carcinogens / Q000493:pharmacokinetics / Q000633:toxicity*; D002478:Cells, Cultured; D005663:Furans / Q000493:pharmacokinetics / Q000633:toxicity*; D008099:Liver / Q000166:cytology / Q000187:drug effects / Q000378:metabolism; D008297:Male; D008930:Mitochondria, Liver / Q000187:drug effects* / Q000378:metabolism; D010085:Oxidative Phosphorylation; D051381:Rats; D011916:Rats, Inbred F344
D002273:Carcinogens; D005663:Furans; D000255:Adenosine Triphosphate; C039281:furan