Effects of chronic ethanol treatment on membrane potential, its electrogenic pump component and Na-K pump activity of cultured rat skeletal myotubes.

Effects of chronic ethanol treatment were examined on transmembrane resting potential (Em), electrogenic pump component of Em and on Na-K pump activity of cultured rat skeletal myotubes. Properties of Na-K pump activity were determined by measurement of [3H]ouabain binding and 86Rb uptake by myotubes after incubation of myotubes in ethanol (217 mM) for up to 9 days. Chronic ethanol exposure caused an increase in Em, an increase in electrogenic pump component of Em and a decrease in depolarizing response to addition of ethanol to the myotubes. Chronic ethanol also produced increases in Na-K pump sites and in Na-K pump activity. Thus, chronic ethanol treatment causes a compensatory increase in amount and activity of the Na-K pump, and this results in an increased expression of the electrogenic pump component of Em. These effects may represent the membrane expression of tolerance to the depressant effects of ethanol.