title: Rho-kinase, but not protein kinase C, is involved in generation of the spontaneous tone in the resting phase of the isolated pig iris sphincter muscle.
abstract: OBJECTIVE
  The purpose of the present study was to clarify the role of Rho-kinase and/or protein kinase C in the resting tension of the isolated pig iris sphincter muscle.
  
  
  METHODS
  The motor activity of the isolated pig iris sphincter muscle was measured isometrically.
  
  
  RESULTS
  EGTA, a chelator of extracellular Ca(2+), significantly reduced the resting tension. Y27632, a Rho-kinase inhibitor, significantly reduced the resting tension in a concentration-dependent manner. The resting tension diminished by Y27632 was significantly recovered by the addition of calyculin A, a myosin light chain phosphatase (MLCP) inhibitor, in a concentration-dependent manner. GF109203X, a protein kinase C inhibitor, had no effect on the resting tension.
  
  
  CONCLUSIONS
  These results suggest that, in the isolated pig iris sphincter muscle, Rho-kinase plays an important role in the generation of spontaneous tone in the resting phase via the inhibition of MLCP activity.
authors.affiliation: Department of Orthoptics and Visual Sciences, School of Health Sciences, Kyushu University of Health and Welfare, Nobeoka, Miyazaki, Japan.
authors.forename: Mayumi
authors.initials: M
authors.lastname: Okano
authors.forename: Yoshikazu
authors.initials: Y
authors.lastname: Uchikawa
authors.forename: Naoko
authors.initials: N
authors.lastname: Tanaka
authors.forename: Junpei
authors.initials: J
authors.lastname: Mutoh
authors.forename: Masamichi
authors.initials: M
authors.lastname: Ohkura
authors.forename: Hiroaki
authors.initials: H
authors.lastname: Hisa
authors.forename: Ryuichi
authors.initials: R
authors.lastname: Yamamoto
mesh_terms: D000818:Animals; D004305:Dose-Response Relationship, Drug; D004791:Enzyme Inhibitors / Q000494:pharmacology; D007498:Iris / Q000201:enzymology*; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000294:innervation / Q000502:physiology*; D043263:Myosin-Light-Chain Phosphatase / Q000037:antagonists & inhibitors / Q000502:physiology; D010275:Parasympathetic Nervous System / Q000502:physiology; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology*; D011680:Pupil / Q000502:physiology; D013552:Swine; D054460:rho-Associated Kinases / Q000037:antagonists & inhibitors / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; D054460:rho-Associated Kinases; D011493:Protein Kinase C; D043263:Myosin-Light-Chain Phosphatase