Aortic smooth muscle cell phenotypic modulation and fibrillar collagen deposition in angiotensin II-dependent hypertension

lBackground: We investigated the effect of nifedipine, AT-1 and ET-1 receptor blockade oil arterial smooth muscle cell phenotypes and collagen deposition in TGRen2 transgenic rat (TGR). Methods: Four-week-old TGR were blood pressure (BP)-matched and allocated to receive a placebo (n=8). the calcium antagonist nifedipine (n=6), the AT-1 specific receptor antagonist irbesartan (n=6), the ETA/ETB antagonist bosentan (n=6) or the ETA-selective antagonist BMS-182874 (n=5). Sprague-Dawley normotensive rats served Lis controls (n=6). After 4 weeks of treatment animals Were euthanized and the left ventricle (LV) and the structural changes in intracardiac arterioles and aorta were assessed histomorphometrically. Smooth muscle cell phenotypes and fibrillar collagen content of the aortic wall were evaluated by immunostaining, using differentiation markers-specific antibodies and Syrius red staining, respectively. The changes in ETA and ETB receptor density were also assessed with quantitative autoradiography. Results: Compared to placebo. only irbesartan lowered BP (P<0.001) and prevented LV and small resistance artery hypertrophy. The aorta of placebo-treated TGR showed all increase in foctal-type smooth muscle cell content and fibrillar collagen staining, compared to controls. These changes were blunted by irbesartan, which increased ETA receptors in the arterial wall, enhanced by BMS-182874 and unaffected by bosentan. Nifedipine also blunted both the VSMC and collagen changes despite having no effect oil BP and ETA receptors. Conclusions: In TGRen2, vascular hypertrophy entails both smooth muscle cell phenotypic modulation and collagen deposition. These alterations do not follow closely the BP challges and seem to imply the dihydropyridine-sensitive calcium channels. (C) 2002 Elsevier Science B.V. All rights reserved.