title: RhoA/Rho-kinase cascade is involved in oxytocin-induced rat uterine contraction.
abstract: The RhoA/Rho-kinase cascade is involved in various cellular functions, including migration, proliferation, and smooth muscle contraction. We examined the potential role of this pathway in oxytocin-induced uterine contraction. The specific Rho-kinase inhibitor Y-27632 inhibited oxytocin-induced rat uterine contraction on d 21 of pregnancy in a concentration-dependent manner, whereas the extent of this inhibition was reduced in the nonpregnant uterus. Y-27632 had no effect on oxytocin-induced intracellular Ca(2+) mobilization in myometrial cells. Immunoblot analysis showed that oxytocin increased the level of myosin light chain phosphorylation, and this increase was attenuated by Y-27632. Oxytocin increased the phosphorylation of myosin-binding subunit of myosin phosphatase, one of the major substrates of Rho-kinase, and this increase was reduced by Y-27632. The expression of Rho-kinase protein was shown to increase in the uterus during pregnancy compared with the nonpregnant uterus, whereas the expression of RhoA protein remained at the same level during pregnancy. RT-PCR and Northern blot analysis showed that the expression of Rho-kinase was up-regulated at the transcriptional level during pregnancy. These results suggest that the RhoA/Rho-kinase pathway may have an important role in oxytocin-induced uterine contraction, and that up-regulation of Rho-kinase is involved in the mechanism underlying the increased contractility of the pregnant myometrium.
authors.affiliation: Osaka University Graduate School of Medicine, Department of Obstetrics and Gynecology, Suita, Osaka 565-0871, Japan. taharam@gyne.med.osaka-u.ac.jp
authors.forename: Masahiro
authors.initials: M
authors.lastname: Tahara
authors.forename: Ken-ichirou
authors.initials: K
authors.lastname: Morishige
authors.forename: Kenjirou
authors.initials: K
authors.lastname: Sawada
authors.forename: Yoshihide
authors.initials: Y
authors.lastname: Ikebuchi
authors.forename: Rikako
authors.initials: R
authors.lastname: Kawagishi
authors.forename: Keiichi
authors.initials: K
authors.lastname: Tasaka
authors.forename: Yuji
authors.initials: Y
authors.lastname: Murata
mesh_terms: D000577:Amides / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000378:metabolism; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D015151:Immunoblotting; D066298:In Vitro Techniques; D007202:Indicators and Reagents; D047908:Intracellular Signaling Peptides and Proteins; D007537:Isometric Contraction / Q000187:drug effects; D018994:Myosin Light Chains / Q000378:metabolism; D010121:Oxytocin / Q000494:pharmacology*; D010766:Phosphorylation; D011247:Pregnancy; D017346:Protein Serine-Threonine Kinases / Q000037:antagonists & inhibitors / Q000235:genetics / Q000502:physiology*; D011725:Pyridines / Q000494:pharmacology; D051381:Rats; D017208:Rats, Wistar; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000187:drug effects*; D014158:Transcription, Genetic; D014590:Uterine Contraction / Q000187:drug effects / Q000502:physiology*; D014599:Uterus / Q000378:metabolism; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*
chemical_list: D000577:Amides; D004791:Enzyme Inhibitors; D007202:Indicators and Reagents; D047908:Intracellular Signaling Peptides and Proteins; D018994:Myosin Light Chains; D011725:Pyridines; C108830:Y 27632; D010121:Oxytocin; D017346:Protein Serine-Threonine Kinases; D054460:rho-Associated Kinases; D020742:rhoA GTP-Binding Protein; D002118:Calcium