Inhibition of red cell Na +, K +-ATPase in digitalized patients

Na +, K +-ATPase activities of the red cells obtained from 75 patients for whom serum digoxin determinations had been ordered are compared with the enzyme activities of the 34 blood samples known not to have been exposed to digitalis. Partial inhibition of the enzyme in a substantial number of samples obtained from patients is observed. These results, in conjunction with previous observations on changes in red cell electrolytes of the digitalized subjects, provide strong support for the assumption that the inhibition of red cell Na +, K +-ATPase may occur in the course of therapy with digitalis.