The effect of ethanol on hepatic sodium plus potassium activated adenosine triphosphatase activity in the rat.

We studied the acute an chronic effects of ethanol on hepatic Na+, K+-ATPase activity. Graded doses of ethanol given 1 h before death acutely increased Na+, K+-ATPase activity in a dose-related manner to a maximum of 138% of control with a simultaneous serum ethanol of 35.4 mM (163 mg%). Rats chronically fed 10% ethanol as their only fluid for 5 days had normal Na+, K+-ATPase activity, however, when ethanol was withdrawn 14 h before death Na+, K+-ATPase activity fell to 60% of control. The in vitro addition of ethanol to membrane preparations from untreated rats caused an increase in Na+, K+-ATPase activity with ethanol concentrations less than 81 mM with decreased activity at higher concentrations. In membranes from rats treated chronically with ethanol Na+, K+-ATPase activity did not respond to in vitro ethanol while the decreased activity noted after ethanol withdrawal was reversed by in vitro ethanol. These results suggest hepatocytes respond to the acute effects of ethanol by membrane adaptation which restores Na+, K+-ATPase activity to normal in the presence of ethanol. This adaptive response is probably due to changes in membrane lipids modulating membrane fluidity.