ERYTHROCYTE NA+-H+ EXCHANGER AND NA+-LI+ COUNTERTRANSPORT ACTIVITY IN PRIMARY ALDOSTERONISM

Several authors have described increased Na-H exchanger activity in essential hypertension but no data are available in secondary forms of hypertension such as primary aldosteronism. We measured Na-H exchanger kinetics together with Na-Li countertransport V-max in the erythrocytes of eight patients with primary aldosteronism and in 15 normotensive control subjects. Plasma aldosterone, plasma renin and plasma potassium were also evaluated. Na-H exchanger V-max appear to be increased in patients with primary aldosteronism and Hill's n, an index of co-operativity amongst intracellular proton binding sites, was significantly lower in patients than in controls. No statistically significant differences were found between affinity for intracellular protons (K50%) and for Na-Li countertransport V-max between the two groups studied. We were unable to find any correlations between Na-H exchanger V-max and Na-Li countertransport V-max in the two groups considered as a whole. From the-present data Na-H exchanger overactivity would not appear to be a specific feature of essential hypertension but seems to be characteristic in patients with primary aldosteronism.