Plasma endothelin is increased in early essential hypertension

Local vascular generation of endothelin-1 (ET-1) may contribute to elevated peripheral resistance in hypertension. We tested the hypothesis that immunoreactive ET production in the forearm circulation is increased in early essential hypertensive subjects. Ten young, previously untreated male patients with mild essential hypertension and no signs of target organ damage were compared with matched normotensive subjects in an outpatient setting. Arterial and venous samples were obtained from indwelling catheters in the brachial artery and the medial cubital vein, respectively. Samples were collected at baseline and after induction of endothelium-dependent (acetylcholine) vasodilation. Immunoreactive ET (ET) was measured after column extraction by a sensitive radioimmunoassay employing a C-terminal ET-1 antibody with negligible cross-reaction to big-ET. Individual recovery rates were determined for each sample. Basal ET was significantly higher in hypertensive than in normotensive subjects, both in venous and arterial samples (P < .01). This difference was also present after correction for recovery (P < .01). There was no significant difference between venous and arterial ET concentrations. Local vasodilation did not change arterial or venous ET levels. In conclusion, plasma ET is increased in young, untreated, essential hypertensive subjects with no signs of target organ damage. The increased circulating immunoreactive ET may point to a role for the peptide early in the development of high blood pressure.