Effect of Acute Ethanol Exposure on Cultured Fetal Rat Hepatocytes: Relation to Mitochondrial Function

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Abstract
Studies from our laboratory have shown that short‐term ethanol exposure inhibits epidermal growth factor‐dependent replication of cultured fetal rat hepatocytes, along with a drop in ATP level, and that these effects could be caused, at least in part, by ethanol‐induced oxidative stress. In these prior studies, mitochondrial morphology was abnormal and membrane lipid peroxidation products were increased, along with reduced transmembrane potential and enhanced permeability to sucrose. To define the effects of ethanol on mitochondrial function further, the present study examines the impact of ethanol exposure on mitochondrial electron transport chain components. A 24‐hr exposure of cultured fetal rat hepatocytes to ethanol (2.5 mg/ml) reduced mitochondrial complex I activity by 16% (p < 0.05), complex IV by 28% (p < 0.05), and succinate dehydrogenase by 23% (p < 0.05). This reduction was paralleled by lower ADP translocase activity (24%, p < 0.05) and diminished mitochondrial glutathione (GSH) (20%, p < 0.05). Pretreatment with 0.1mm S‐adenosyl methionine, before ethanol exposure, normalized mitochondrial GSH along with activities of complex I, complex IV, and succinate dehydrogenase. A 3‐hr exposure of isolated mitochondria (which do not metabolize ethanol) to ethanol (2.5 mg/ml), inhibited the activities of complex I (19%, p < 0.05), complex IV (24%, p < 0.05), and of ATP synthesis (20%, p < 0.05). It is concluded that: (1) short‐term ethanol exposure modestly decreases ATP synthesis by inhibiting activities of fetal hepatic mitochondrial electron transport chain components; (2) ethanol, in the absence of acetaldehyde (as in the isolated mitochondria), can directly impair mitochondrial respiratory chain components; and (3) protection from some of the adverse effects of ethanol by pretreatment with S‐adenosyl methionine suggests that these effects are secondary to depletion of mitochondrial GSH.