Na-K-ATPase in erythrocyte ghosts is not a marker for primary hypertension

In search for a diagnostic marker for essential hypertension, we investigated the activity of the ouabain sensitive Na-K-ATPase and the ouabain insensitive ATPase in erythrocyte ghosts of 57 patients with essential hypertension, 12 patients with renal hypertension, 6 patients with Cushing's syndrome and 4 patients with primary hyperaldosteronism. Na-K-ATPase-activity was increased in patients with essential hypertension and in patients with renal hypertension compared with controls with a considerable overlap. Na-K-ATPase-activity was increased in all patients with Cushing's syndrome but was not different from the control group in patients with Conn's syndrome. Ouabain-insensitive ATPase-activity was similar in all patients and in normotensive controls. The serum of patients with essential hypertension did not exhibit an ouabain-like ATPase-inhibiting activity when incubated with erythrocyte ghosts of normotensive controls. In our hands, determination of the Na-K-ATPase-activity in erythrocyte ghosts cannot be used as a diagnostic marker for essential hypertension.