VASCULAR RENIN-ANGIOTENSIN SYSTEM AND SYMPATHETIC NERVOUS-SYSTEM ACTIVITY IN HUMAN HYPERTENSION

Experimental data indicate the existence of a vascular tissue renin-an giotensin system in several different vessels from various animal mode ls. Active renin can be locally synthesized into the vessel wall or ta ken up from circulating plasma to produce vascular angiotensin II. Usi ng the human forearm technique, we produced evidence indicating the re lease of active and inactive renin and of angiotensin II from the vess els of hypertensive patients. Moreover, the production of vascular ang iotensin II seems to be strictly correlated to the circulating renin p rofile, suggesting the possibility that vascular renin might be at lea st partially taken up from plasma. To investigate a possible function of the vascular renin-angiotensin system, we studied its interaction w ith sympathetic neurotransmission in essential hypertensive patients. In line with animal studies, vascular angiotensin II increases the vas oconstriction induced by the stimulation of the sympathetic nervous sy stem through the potentiation of noradrenaline release at a presynapti c level, and this effect seems to be mediated by beta-adrenoceptor act ivation. This facilitating effect on sympathetic neurotransmission exe rted by vascular angiotensin II can be antagonized by both angiotensin II antagonists and angiotensin-converting enzyme inhibitors.