Sodium/lithium countertransport and intracellular calcium concentration in patients with essential hypertension and coronary heart disease.

The present study was designed to test the hypothesis that enhanced intracellular calcium signalling and increased sodium/lithium countertransport (Na(+)/Li(+) CT) activity may be associated with coronary heart disease (CHD) in non-diabetic patients with essential hypertension. Platelet-activating factor (PAF)-evoked rises in the intracellular calcium concentration ([Ca(2+)](i)) were measured in Epstein-Barr-virus-immortalized lymphoblasts from 62 hypertensive patients with CHD and 34 patients without CHD. Na(+)/Li(+) CT activity was assessed in erythrocytes from 80 hypertensive patients with CHD and 46 patients without CHD. Baseline values of unstimulated and PAF-stimulated [Ca(2+)](i) were not significantly different between hypertensive subjects with (baseline, 126+/-5 nmol/l; stimulated, 550+/-43 nmol/l) and without (baseline, 125+/-5 nmol/l; stimulated, 654+/-105 nmol/l) CHD. Similarly, Na(+)/Li(+) CT activity was not significantly different between the two groups (patients with CHD, 219+/-8 micromol x l(-1) x h(-1); patients without CHD, 234+/-10 micromol x l(-1) x h(-1)). We conclude that intracellular signal transduction, as indicated by PAF-induced rises in [Ca(2+)](i) and Na(+)/Li(+) CT activity, is not associated with an increased risk of CHD in non-diabetic patients with essential hypertension.