Ethanol-induced free radicals and hepatic DNA strand breaks are prevented in vivo by antioxidants: effects of acute and chronic ethanol exposure

Ethanol was given to male Wistar rats as an acute dose (5 g/kg) or continuo usly at 5% (w/v) in a liquid diet to provide 36% of the caloric requirement . Free radicals generated in the liver were collected as a stable adduct in bile following the irt vivo administration of the spin trapping agent alph a-(4-pyridyl-1-oxide)-N-tert-butylnitron (POBN; 700 mg/kg), [1-C-13]ethanol was used to confirm the formation of the 1-hydroxyethyl radical and to dem onstrate that this was ethanol-derived in the case of the single-dose treat ment, Free radical production increased up to 1h after the acute dose and t hen plateaued over the next 30 min. During chronic exposure to ethanol, fre e radical generation increased significantly after 1 week and then declined again to remain at a low level over the next 2 weeks; this transient incre ase corresponded closely with the induction of cytochrome P-450 2E1 (CYP 2E 1) in response to ethanol feeding. Single-cell electrophoresis was used to investigate effects on DNA, After an acute dose of ethanol, the frequency o f single-strand breaks increased from 1 h to peak at 6 h but then declined again to control values by 12 h, During the chronic exposure, an increase i n the frequency of DNA breaks was seen at 3 days, reached a peak at 1 week and then decreased slowly over the next 5 weeks. The effects of antioxidant s on these parameters was investigated after an acute dose of ethanol, Pret reatment with vitamin C (400 mg/kg, i.p., daily for 5 days) or vitamin E (1 00 mg/kg, i.p., for 5 days) prior to the administration of ethanol (5 g/kg) inhibited generation of the 1-hydroxyethyl-POBN adduct by 30 and 50%, resp ectively, and both agents prevented the increased frequency of DNA single-s trand breaks caused by ethanol, The significance of the temporal coincidenc e of changes in the above parameters in response to ethanol is discussed.