Sodium-potassium-dependent ATPase activity in erythrocyte ghosts of patients with primary and secondary hypertension.

1. We have investigated the function of the Na+-K+ pump in the erythrocytes of patients with various types of hypertension by measuring the activity of ouabain-sensitive Na+-K+-dependent ATPase and ouabain-insensitive ATPase in the erythrocyte ghosts of these patients. 2. Mean Na+-K+-ATPase activity was increased threefold in six patients with Cushing's syndrome and hypertension (0.985 +/- SD 0.288 mumol of phosphate h-1 mg-1) compared with that in 49 control subjects (0.334 +/- 0.147 mumol of phosphate h-1 mg-1) (P < 0.0025), but not in four patients with primary aldosteronism (0.278 +/- 0.108 mumol of phosphate h-1 mg-1). 3. Na+-K+-ATPase activity slightly exceeded the control range in 57 patients with primary hypertension (0.410 +/- 0.245 mumol of phosphate h-1 mg-1; P < 0.025) and in 12 patients with renal hypertension (0.475 +/- 0.250 mumol of phosphate h-1 mg-1) (P < 0.025). 4. There was no difference in ouabain-insensitive ATPase between the controls and the different types of hypertension. 5. The data support the hypothesis of an activation of the Na+ pump in patients with glucocorticoid excess. This helps to explain previous observations of a redistribution of sodium and water to the extracellular compartment in experimental glucocorticoid-induced hypertension.