Antagonists, inhibitors and antisera in the evaluation of vascular renin activity. The role of local generation of angiotensin II.

It is well established that the arterial wall contains renin-like material. It is suggested that this renin generates significant quantities of angiotensin II (AII) which occupy vascular AII receptors. This is important in determining the pressor response to exogenous AII and in the maintenance of blood pressure. Four lines of evidence support this view. (a) Prevention of AII generation by nephrectomy or converting enzyme inhibition increases the pressor response to AII which then becomes independent of sodium balance. (b) AII antagonists are more effective in renin-mediated hypertension than AII antisera. (c) Changes in renin-mediated pressor responsive to AII after bilateral nephrectomy take a much longer time to occur than can be explained in terms of changes in circulating renin activity: these changes are also observed in isolated vessels. (d) The depressor response to antagonist and inhibitors is preserved after bilateral nephrectomy for much longer periods than can be accounted for by circulating levels of renin.