ROLE OF L-ARGININE NITRIC-OXIDE PATHWAY IN HYPERTENSION

Objective: The present study was designed to investigate the effect Of L-arginine administration on patients with essential and secondary hy pertension by measuring haemodynamic parameters, neuroendocrine hormon es and indicators of nitric oxide (NO) release. Design: Ten patients w ith essential hypertension and six with secondary hypertension (three with renovascular hypertension and three with primary aldosteronism) w ere enrolled in the study. Methods: L-Arginine was administered intrav enously to the hypertensive patients. During L-arginine administration , blood pressure, heart rate, cardiac output and neuroendocrine hormon es such as catecholamines, plasma renin activity and plasma aldosteron e were measured. To examine whether L-arginine administration increase s NO production, indicators of NO release in vivo such as plasma cycli c GMP, plasma citrulline and urinary excretion of nitrite and nitrate were measured simultaneously. Results: During administration, mean art erial pressure decreased, heart rate increased, cardiac output increas ed and total peripheral resistance decreased. The indicators of NO rel ease increased simultaneously during administration. Catecholamine and plasma renin activity, rather than increasing in response to L-argini ne-induced hypotension as expected, showed no significant changes exce pt in patients with renovascular hypertension. In all patients plasma aldosterone levels decreased significantly in response to L-arginine a dministration, regardless of basal plasma renin activity and aldostero ne levels. Conclusions: These results suggest that exogenous L-arginin e produces a vasodilatory effect by increasing NO production and that L-arginine, or released NO, modulates the release of neuroendocrine ho rmones in hypertensive subjects.