Angiotensin II stimulates extracellular signal-regulated kinase activity in intact pressurized rat mesenteric resistance arteries

The activation of extracellular signal-regulated kinases 1/2 (ERK1/2) was assessed in isolated rat mesenteric resistance arteries (200-mum diameter) in a pressure myo,myograph and stimulated for 5 minutes by angiotensin II. (Ang II, 0.1 mu mol/L) with a pressure of 70 mm Hg. ERK1/2 activity was measured by using an in-gel assay, and ERK1/2 phosphorylation was measured by Western blot analysis with use of a phospho-specific ERK1/2 antibody. Ang II (0.1 mu mol/L) induced contraction (28% of phenylephrine contraction, 10 mu mol/L). ERK kinase inhibitor PD98059 (10 mu mol/L) attenuated this contraction by 36% but not that to phenylephrine or K+ (60 mmol/L), In unpressurized arteries, Ang II increased ERK1/2 activity by 26%, and pressure (70 mm Hg) itself increased ERK1/2 activity by 72%. Ang II and pressure together acted synergistically, increasing ERK1/2 activity by 264%. Thus, in pressurized vessels, Ang IT (0.1 mu mol/L) increased ERK1/2 activity by 112%. calculated as [(364/172)-1] X 100, which was confirmed by a measured 72% increase in ERK1/2 phosphorylation. Ang II type 1 receptor blockade by candesartan (10 mu mol/L) abolished the Ang II-induced increase in ERK1/2 activity, but Ang II type 2 receptor blockade (PD 123319, 10 mu mol/L) did not. The Ang II-induced increase in ERK1/2 activity was inhibited by protein kinase C inhibitors Ro-31-8220 (1 mu mol/L) and Go-6976 (300 nmol/L) and tyrosine kinase inhibitors genistein (1 mu mol/L, general) and herbimycin A (1 mu mol/L, c-Src family). The present findings show for the first time in intact resistance arteries that ERK1/2 activation is rapidly regulated by Ang III is synergistic with pressure, and is involved in contraction. The ERK1/2 signaling pathway apparently includes upstream protein kinase C and c-Src.