title: Rho-kinase inhibitor inhibits both myosin phosphorylation-dependent and -independent enhancement of myofilament Ca2+ sensitivity in the bovine middle cerebral artery.
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.
authors.affiliation: Division of Molecular Cardiology, Research Institute of Angiocardiolgoy, Graduate School of Medical Sciences, Kyushu University, 3-1-1 Maidashi, Higashi-ku, Fukuoka 812-8582, Japan.
authors.forename: Yoshihisa
authors.initials: Y
authors.lastname: Maeda
authors.forename: Katsuya
authors.initials: K
authors.lastname: Hirano
authors.forename: Junji
authors.initials: J
authors.lastname: Nishimura
authors.forename: Tomio
authors.initials: T
authors.lastname: Sasaki
authors.forename: Hideo
authors.initials: H
authors.lastname: Kanaide
mesh_terms: D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid / Q000494:pharmacology; D008841:Actin Cytoskeleton / Q000187:drug effects* / Q000378:metabolism; D000577:Amides / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism*; D002417:Cattle; D004791:Enzyme Inhibitors / Q000494:pharmacology; D066298:In Vitro Techniques; D047908:Intracellular Signaling Peptides and Proteins; D020768:Middle Cerebral Artery / Q000187:drug effects* / Q000378:metabolism; D009218:Myosins / Q000378:metabolism*; D010766:Phosphorylation / Q000187:drug effects; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors* / Q000378:metabolism; D011725:Pyridines / Q000494:pharmacology; D014661:Vasoconstriction / Q000187:drug effects / Q000502:physiology; D054460:rho-Associated Kinases
chemical_list: D000577:Amides; D004791:Enzyme Inhibitors; D047908:Intracellular Signaling Peptides and Proteins; D011725:Pyridines; C108830:Y 27632; D019796:15-Hydroxy-11 alpha,9 alpha-(epoxymethano)prosta-5,13-dienoic Acid; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D009218:Myosins; D002118:Calcium