Vascular tissue renin-angiotensin system in hypertensive humans.

Aim: To obtain direct evidence for and evaluate functional aspects of the vascular tissue renin-angiotensin system. Methods: The local release of renin and angiotensin II was studied in forearm and coronary vascular beds of hypertensive hospitalized patients. The interaction between the vascular tissue renin-angiotensin system and sympathetic neurotransmission was also evaluated. Results: Local β-adrenoceptor stimulation released active and inactive renin and angiotensin II from forearm vessels, indicating the presence of a vascular tissue renin-angiotensin system in essential hypertensives. Local production of active renin and angiotensin II was closely correlated with circulating renin levels, suggesting that this vascular tissue renin-angiotensin system is at least partly dependent on uptake of renin from the circulating renin-angiotensin system. The local active renin and angiotensin II production was rapidly exhausted; this might represent a short-term control mechanism. Locally generated angiotensin II increased sympathetic vasoconstriction through the presynaptic release of noradrenaline and this effect was mediated by β-adrenoceptor stimulation. Infusions of adenosine promoted the release of active renin and angiotensin II from the forearm and the coronary vessels.