Circulating angiotensin influences vascular tone via its receptors particularly at the precapillary vessels. In addition, an intrinsic renin-angiotensin system has been postulated to exist in vascular wall. In this study, we documented components of the renin-angiotensin system in cultured vascular smooth-muscle cells. These cells are capable of angiotensin formation. Approximately 50% of the angiotensin-generating activity is neutralized by a renin-specific antibody. Immunoaffinity-purified vascular renin has a pH optimum of 6.8 and a molecular weight of 38,000. The intracellular renin concentration increases fourfold when cultured in serum-free media for 48 h, suggesting physiological regulation by serum factor(s). Cultured vascular smooth-muscle cells also contain angiotensinogen and immunoreactive angiotensins. We postulate that these elements constitute an intrinsic system that exerts an autocrine or paracrine influence on local vascular function, including vascular tone.
Angiotensin I Angiotensin II