Effects of ethanol on ion transport in muscle membranes.

Alterations in the function of cardiac cellular membranes may contribute to the pathogenesis of abnormal cardiac function after both acute and chronic administration of ethanol. Both the sarcolemmal sodium pump-derived Na+,K+-ATPase and the calcium pump of the sarcoplasmic reticulum are inhibited by ethanol, although inhibitory effects at concentrations that can be reached in humans are seen only under special conditions. Abnormalities in both the Na+,K+-ATPase and calcium pump have been observed after chronic ethanol ingestion, and there is evidence that chronic ethanol ingestion reduces the sensitivity of these activities to ethanol added in vitro. The acute effects of ethanol on these membrane activities appear to be related to an increase in membrane fluidity, whereas the altered functional state of membranes produced by chronic ethanol ingestion may reflect alterations in membrane lipids, possibly associated with a decrease in membrane fluidity.