Involvement of rho-kinase and the actin filament network in angiotensin II-Induced contraction and extracellular signal-regulated kinase activity in intact rat mesenteric resistance arteries

We have previously shown that angiotensin II (Ang II) and pressure increase extracellular signal-regulated kinase (ERK) 1/2 activity synergistically i n intact, pressurized resistance arteries in vitro. However, the mechanisms by which pressure and Ang II activate ERK1/2 in intact resistance arteries remain to be determined. The purpose of the present study was to investiga te. the involvement of Rho-kinase and the actin filament network in Ang II- and pressure-induced ERK1/2 activation, as well as in the contractile resp onse induced by Ang II. Mesenteric resistance arteries (200 to 300 mum) wer e isolated, mounted in an arteriograph, and stimulated by pressure, Ang II, or both. Activation of ERK1/2 was then measured by an in-gel assay. In mes enteric resistance arteries maintained at 70 min Hg, Ang II (0.1 mu mol/L) induced contraction (29 +/-1.4% of phenylephrine, 10 mu mol/L-induced contr action) and significantly increased ERK1/2 activity. Selective inhibition o f Rho-kinase by Y-27632 (10 mu mol/L and selective disruption of the actin filament network by cytochalasin B (10 mu mol/L) both decreased the Ang II- induced contraction by 78 +/-1.2% and 87 +/-1.9%, respectively, and signifi cantly diminished ERK1/2 activity. In the absence of Ang II, increasing int raluminal pressure from 0 to 70 or 120 mm Hg increased ERK 1/2 activity. ER K1/2 activity at 120 mm Hg was similar to that observed at 70 mm in the pre sence of Ang IL Pressure-induced ERK1/2 activation was markedly attenuated by cytochalasin B but not by Y-27632. These results indicate that whereas p ressure-induced ERK1/2 activation requires an intact actin filament network , but not Rho-kinase, the activation of ERK1/2 and the contraction induced by Ang II require both Rho-kinase and an intact actin filament network in i solated, intact mesenteric resistance arteries.