The major objective of the proposed research is to characterize further the effects of acute and chronic ethanol administration on hepatic detoxification processes. Previous observations have show that ethanol affects hepatic glutathione metabolism. Chronic ethanol feeding increases hepatic turnover of GSH by increasing sinusoidal efflux of GSH from the liver. Acute ethanol administration can impair synthesis of GSH from its precursor amino acid, methionine. Since glutathione is important in several cellular detoxification processes, these changes could alter the capacity of cells to prevent injury from reactive drug metabolites, toxic oxygen species and free radicals. The hypothesis to be tested is that chronic ethanol feeding increases hepatic requirements for glutathione by increasing its loss through non- detoxification pathways. The mechanism of the observed increase fed rats will be examined in primary hepatocyte cultures, liver perfusions, and sinusoidal membrane vesicles, and vesicles from ethanol-fed rats. To avoid confounding acute effects of ethanol, one group of ethanol fed rats will be studied 24 hrs after withdrawal. Both pair fed and ad lib chow fed animals will be used as controls. Additional experiments will address the consequences of altered glutathione metabolism by examining the capacity of the ethanol-fed liver to withstand additional stresses such as fasting, electrophilic insults and oxidative stress. To understand better the perivenular predominance of alcoholic liver injury, changes in zonal distribution of glutathione- dependent detoxification enzymes, superoxide dismutase, and xanthine oxidase will be examined after ethanol feeding. These studies will utilize histochemical and immunohistochemical techniques to confirm the distribution of these enzymes and to look for changes which may occur during adaptation to chronic ethanol feeding. Finally, the role of glutathione in detoxification of acetaldehyde will be explored to determine whether ethanol-related changes in glutathione metabolism may be related to the pathogenesis of alcoholic liver injury. Since glutathione has a pivotal role in cellular detoxification in many tissues, characterization of these changes may improve our understanding of how ethanol can cause tissue injury in a large number of organs.
