ANGIOTENSIN-II INDUCES VASCULAR SMOOTH-MUSCLE CELL REPLICATION INDEPENDENT OF BLOOD-PRESSURE

The purpose of this investigation was to evaluate the role of blood pr essure in the proliferative response of vascular smooth muscle cells t o systemic infusion of angiotensin II (Ang II). Our laboratory has pre viously shown that infusion of Ang II induces smooth muscle cell proli feration in rat mesenteric vessels and carotid arteries. Ang II, a str ong vasopressor, raised systolic blood pressure in rats from 120 to 20 0 mm Hg at a dose of 435 ng.kg(-1).min(-1) after 1 week of treatment. The question arises as to whether this development of hypertension is a primary contributor to the replicative activities observed in the ar terial wall of the mesenteric arteries or the carotid arteries or whet her Ang II alone, without an increase in blood pressure, is sufficient to stimulate proliferation in these vessels. In the previous studies, we found that Ang II stimulated smooth muscle cell replication in the carotid artery and in type III and type I mesenteric microvessels. Th is study demonstrates that although administration of hydralazine norm alizes the animals' blood pressures, it does not suppress the mitogeni c effect of Ang II. Thus, it appears that Ang II has a direct effect o n cell proliferation.