Previously, we and others have shown that angiotensin II enhances vascular smooth muscle cell extracellular matrix synthesis via stimulation of the angiotensin II type 1 (AT1) receptor. Recently, expression of the type 2 (AT2) receptor has been confirmed in the adult vasculature, but its role has not yet been fully defined. The aim of the present study was to examine the effects of stimulation of AT2 receptors on collagen synthesis in vascular smooth muscle cells. Retroviral gene transfer was used to supplement adult vascular smooth muscle cells with AT2 receptors to mimic the vasculature in vivo. The treatment of these cells with the AT2 receptor agonist CGP42212A (10-7 mol/L) alone did not cause a significant change in p42/p44 MAP kinase activity but caused a modest (30% to 50%) decrease in protein tyrosine phosphatase activity. Treatment with CGP42112A also caused a dose- and time-dependent increase in both cell-associated and secretory collagen synthesis (148±17% of control at 48 hours, P<0.05), which was completely inhibited by the AT2 receptor antagonist PD123319, unaffected by the AT1 receptor antagonist losartan, and attenuated by treatment with pertussis toxin or G(αi) antisense oligonucleotides. Interestingly, studies in other cell lines demonstrated that CGP42112A caused similar results in transfected mesangial cells but had essentially opposite effects in fibroblasts (NIH-3T3-AT2). These results suggest that AT2 receptor stimulation can increase collagen synthesis in vascular smooth muscle cells via a G(αi-mediated) mechanism and provide evidence for heterogeneity in the effects of AT2 receptor stimulation in different tissues.
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