ADAPTIVE-CHANGES INDUCED BY CHRONIC ETHANOL INGESTION ON HEPATIC MITOCHONDRIAL AND MICROSOMAL-ENZYME ACTIVITIES

Ethanol exerts its pharmacological effects by altering the physico-che mical properties of biological membranes. Modifications induced by eth anol may result in changes in the activity of membrane-bound enzymes t hat have been shown to require a specific membrane fluidity and compos ition for optimal function. In this study we have carried out the anal ysis of the effects of ethanol on the different enzyme activities of h epatic microsomes and mitochondria. Our results show that chronic etha nol treatment causes marked changes to enzyme activity in the mitochon drial and microsomal electron-transport systems in chick liver. The in hibition observed in the mitochondrial enzyme activities studied, indi cates that ethanol ingestion depresses the functionality of the respir atory-chain. In microsomes, NADH cytochrome c reductase activity was s ignificantly decreased whilst NADH cytochrome b(5) reductase activity was increased after ethanol administration. Hepatic mitochondria and m icrosomes from control and chronic ethanol-treated chicks were submitt ed to ethanol in vitro in order to study the possible existence of ada ptive changes in the different enzyme systems as consequence of long-t erm ethanol administration. Incubation of control membranes with diffe rent amounts of ethanol induced marked alterations in enzyme activitie s. In membranes isolated from ethanol-treated chicks, ethanol also pro duced a similar effect except with cytochrome oxidase and NADH cytochr ome b(5) reductase, which resisted alteration by ethanol added, sugges ting the existence of adaptive changes in these enzyme activities that allow them to remain unaltered after exposure to ethanol in vitro.