Vascular renin-angiotensin system: the unanswered questions.

Study of the vascular renin-angiotensin system can be approached in a number of ways. The capacity of the blood vessel to generate angiotensin II, when exposed to angiotensinogen, immunocytochemical demonstration of renin, the presence of renin mRNA and functional changes attributable to local generation of angiotensin have all been used. Although each of these techniques requires careful and critical examination from the standpoint of specificity and sensitivity, there is now strong evidence for a functionally important system in the arterial wall. The relative importance of uptake and local synthesis and the physiological role of this system, as distinct from the renal renin system, still remains to be elucidated.