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 a ssessed in isolated rat mesenteric resistance arteries (200-mum diameter) i n 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 meas ured by using an in-gel assay, and ERK1/2 phosphorylation was measured by W estern 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 m u mol/L). ERK kinase inhibitor PD98059 (10 mu mol/L) attenuated this contra ction by 36% but not that to phenylephrine or K+ (60 mmol/L), In unpressuri zed 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 a cted synergistically, increasing ERK1/2 activity by 264%. Thus, in pressuri zed vessels, Ang IT (0.1 mu mol/L) increased ERK1/2 activity by 112%. calcu lated as [(364/172)-1] X 100, which was confirmed by a measured 72% increas e 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, bu t 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 i nhibitors Ro-31-8220 (1 mu mol/L) and Go-6976 (300 nmol/L) and tyrosine kin ase 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 res istance arteries that ERK1/2 activation is rapidly regulated by Ang III is synergistic with pressure, and is involved in contraction. The ERK1/2 signa ling pathway apparently includes upstream protein kinase C and c-Src.