An in vivo study of cation transport in essential hypertension.

In order to study cation transport in vivo the changes in plasma and red cell rubidium concentrations were measured following an oral load of rubidium chloride. Eight patients receiving short-term digoxin therapy, 10 patients with chronic renal failure and 22 patients with untreated essential hypertension were studied, and the findings were compared with those in healthy control subjects matched for age, sex, race, obesity index, and plasma and red cell potassium concentrations. In patients receiving short-term digoxin therapy, and in patients with chronic renal failure, the increases in plasma rubidium concentrations after the oral load of rubidium chloride were significantly enhanced and the increases in red cell rubidium concentrations were significantly attenuated. These findings are consistent with a generalized reduction in Na+, K+-ATPase activity in vivo. In contrast, in patients with untreated essential hypertension the increases in both plasma and red cell rubidium concentrations following the oral load were significantly enhanced. These data do not support the hypothesis that essential hypertension is associated with reduced Na+, K+-ATPase activity in vivo, at least in the red cell.