Effect of Aldosterone on the Human Erythrocyte Sodium-Potassium Pump in vitro

1. The effects of aldosterone in vitro on the Na⁺,K⁺-dependent ATPase activity of isolated human erythrocyte membranes and on rubidium (⁸⁶Rb) uptake and [³H]ouabain binding of intact erythrocytes were studied.

2. ATPase activity was nearly doubled (0.061 ± 0.006 to 0.110 ± 0.01 μmol of P_l h⁻¹ mg⁻¹ of protein) by the addition of a physiological concentration of aldosterone (2.7 × 10-¹⁰ mol/l). Higher concentrations had no greater effect.

3. Aldosterone had no significant effect on ⁸⁶Rb uptake or [³H]ouabain binding.

4. Erythrocytes contain aldosterone at concentrations similar to that in plasma. The effect of aldosterone on ATPase is probably maximal.