Abstract
The role of Rho kinase in Ca2+ sensitization of the contractile apparatus in smooth muscle was investigated in the bovine middle cerebral artery. U46619, a thromboxane A2 analog, induced a greater sustained contraction with a smaller [Ca2+]i elevation than that seen with 118 mm K+. The level of myosin light chain (MLC) phosphorylation obtained in the initial phase of the contraction was higher than that seen with 118 mm K+; thereafter, it gradually declined to a comparable level in the late phase. During the steady state of the U46619-induced contraction, Y27632 (10 microM), a Rho-kinase inhibitor, partially inhibited [Ca2+]i, although it substantially inhibited tension and MLC phosphorylation. Wortmannin (10 microM), an MLC kinase inhibitor, had no significant effect on [Ca2+]i, but it completely inhibited MLC phosphorylation and partially inhibited tension. The wortmannin-resistant tension development was thus not associated with MLC phosphorylation, and this component was completely inhibited by Y27632. In conclusion, U46619 enhanced Ca2+ sensitivity in a manner both dependent and independent of MLC phosphorylation in the bovine middle cerebral artery. Both mechanisms of Ca2+ sensitization can be inhibited by the Rho-kinase inhibitor.
Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Disclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.