Involvement of Rho and Rho-associated kinase in sphincteric smooth muscle contraction by angiotensin II

The tonic smooth muscles of lower esophageal sphincter (LES) and internal anal sphincter (IAS) are subject to modulation by the neurohumoral agents. We report that anglotensin (Ang)II-induced contraction of rat IAS and LES smooth muscle cells (SMC) was inhibited by Clostridium botulinum, C3 exozyme, HA 1077 and Y 27632, suggesting a role for Rho kinase and a Rho-associated kinase (ROK). Ang II-induced contraction of the SMC was also attenuated by genistein, antibodies to the pp60(c-src), P-190 RhoGTPase-activating protein (p(190) RhoGAP), carboxyl terminus of Galpha(13), carboxyl terminus peptide, and ADP ribosylation factor (ARF) antibody. Ang II-induced increase in p(190) RhoGAP tyrosine phosphorylation was attenuated by genistein. Furthermore, Ang II-induced increase in smooth muscle tone and phosphorylation of myosin light chain (MLC; 20 kDa; MLC20-P) were attenuated by Y 27632 and genistein. The results suggest an important role for Galpha(13) and pp60(c-src) in the intracellular events responsible for the activation of RhoA/ROK in Ang II-induced contraction of LES and IAS SMC.