Intracellular cations and transmembrane cation transport in essential hypertension: the importance of controlled clinical observations.

We measured Na+, K+ and total Ca2+ concentrations as well as first order efflux rate constants for Na+ and Ca2+ in red cells from 22 patients with untreated essential hypertension and 22 normotensive control subjects. Both groups were individually and prospectively matched for age, sex and weight. Intracellular Na+ and K+ were also measured in a separate population consisting of 31 hypertensive patients and 41 normotensive subjects who were not matched. In order to test for possible plasma inhibitors of Na+ or Ca2+ transport in hypertension, Na+ and Ca2+ efflux rate constants in 15 paired patients were measured in red cells which were incubated in either homologous or paired plasma. Intracellular Na+ and K+ concentrations and Na+ and Ca2+ efflux rate constants were similar in the matched subjects. Significant positive correlations were found between intracellular Na+ and body weight (r = 0.27, P = 0.041) and between intracellular K+ and age (r = 0.29, P = 0.028). In the unmatched population intracellular Na+ correlated significantly with age (r = 0.25, P = 0.029) and was significantly increased in hypertensive patients. This difference was due wholly to increased intracellular Na+ in hypertensive females. After correction for age and weight, intracellular Na+ was similar in both hypertensive and normotensive subjects. Intracellular K+ did not differ between these groups but was significantly lower in males. Intracellular Ca2+ was similar in the matched groups after correction for age and weight, but the regression equations containing age and weight as independent variables were significantly different in hypertensive and normotensive subjects.(ABSTRACT TRUNCATED AT 250 WORDS)