Increase in Na⁺,K⁺-ATPase activity of erythrocytes and skeletal muscle after chronic ethanol consumption: Evidence for reduced efficiency of the enzyme

Increased Na⁺,K⁺-ATPase activity observed after chronic ethanol consumption has been examined to determine whether the increase is due to changes in the kinetic properties of the enzyme or increases in the amount of enzyme in the membranes examined. In skeletal muscle and erythrocyte ghosts from rat, as well as from humans, increased Na⁺,K⁺-ATPase activity in ethanol-consuming individuals was not accompanied by an increase in the number of ouabain binding sites. In studies with intact human erythrocytes, similar ouabain-sensitive ²²Na⁺ and ⁸⁶Rb⁺ pumping rates were observed between normal and ethanol-consuming individuals and the Na⁺ to Rb⁺ pumping ratio was found to be 1.5 in all cases. However, ouabain-sensitive lactate plus P(i) formation was increased in cells from alcoholic individuals. Thus these data suggest that increased enzyme activity may be due to a kinetic alteration of the Na⁺,K⁺-ATPase and that the enzyme may be less efficient in coupling ion pumping to ATP hydrolysis than the enzyme in normal cells.