Decreased Na/K ATPase ouabain binding sites in red blood cells of patients with insulin-dependent diabetes and healthy north African control subjects: relationship with diabetic neuropathy.

Like other degenerative complications occurring during diabetes, development of neuropathy is determined mainly by the duration of disease and quality of control. However, there may be some predisposing factors. Activity of Na/K ATPase has been implicated in the pathophysiology of diabetic neuropathy. A decrease in the activity of this enzyme has been observed in red blood cells of poorly controlled diabetic patients and healthy North African subjects who are predisposed to diabetic neuropathy. This study was performed to characterize abnormalities of Na/K ATPase activity in these two populations. For this purpose we measured enzyme activity (hydrolysis of ATP) and the number of enzyme units (number of binding sites for ouabain) in the red blood cells of three groups of men, i.e., healthy Caucasian subjects, healthy North African subjects and Caucasian insulin-dependent diabetic patients. The level of Na/K ATPase activity and the number of enzyme units were about 30% lower in the red blood cells of diabetic patients and North African subjects, than in healthy Caucasian controls. In healthy North African subjects predisposed to neuropathy in case of development of diabetes, the decrease in enzymatic activity was correlated with a decrease in the number of enzyme units. This correlation was not observed in diabetic patients. We speculate that the constitutional decrease in Na/K ATPase activity in healthy North African subjects corresponds to a quantitative defect, whereas the acquired decrease in diabetic patients corresponds to a qualitative defect probably related to the structure of the lipid membrane.