Sodium-potassium-ATPase activity is influenced by ethnic origin and not by obesity

Previous investigations have suggested that red-cell ouabain binding (an indirect measure of sodium-potassium-ATPase activity) is lower in severely obese patients than in normal controls. We now confirm that ouabain binding measures sodium-potassium-ATPase activity, and we demonstrate that the level of this activity is genetically determined. The activity of this enzyme differs in various ethnic and racial groups, relatively high levels being encountered in non-Jewish white subjects, particularly those with some Scandinavian ancestry. On the other hand, black, Asian, and Jewish white subjects have lower sodium-potassium-ATPase activity. In contrast, no difference was found in red-cell sodium-potassium-ATPase activity between severely obese and normal persons, nor could we confirm a putative effect of food intake on the level of the red-cell enzyme. We suggest that in most earlier studies in which differences were found between normal and severely obese persons, those differences could have been due to differences in the ethnic origins of the obese and control populations.