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 μmol of phosphate h⁻¹ mg⁻¹) compared with that in 49 control subjects (0.334 ± 0.147 μmol of phosphate h⁻¹ mg⁻¹) (P<0.0025), but not in four patients with primary aldosteronism (0.278 ± 0.108 μmol 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 μmol of phosphate h⁻¹ mg⁻¹; P<0.025) and in 12 patients with renal hypertension (0.475 ± 0.250 μmol 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.