RhoA/Rho-kinase cascade is involved in oxytocin-induced rat uterine contraction

• Published in: Endocrinology (Philadelphia) 2002-03, Vol.143 (3), p.920-929
• Main Authors: Tahara, Masahiro, Morishige, Ken-ichirou, Sawada, Kenjirou, Ikebuchi, Yoshihide, Kawagishi, Rikako, Tasaka, Keiichi, Murata, Yuji
• Format: Article
• Language: English
• Subjects: Amides - pharmacology; Animals; Calcium - metabolism; Enzyme Inhibitors - pharmacology; Female; Immunoblotting; In Vitro Techniques; Indicators and Reagents; Intracellular Signaling Peptides and Proteins; Isometric Contraction - drug effects; Myosin Light Chains - metabolism; Oxytocin - pharmacology; Phosphorylation; Pregnancy; Protein-Serine-Threonine Kinases - antagonists & inhibitors; Protein-Serine-Threonine Kinases - genetics; Protein-Serine-Threonine Kinases - physiology; Pyridines - pharmacology; Rats; Rats, Wistar; Reverse Transcriptase Polymerase Chain Reaction; rho-Associated Kinases; rhoA GTP-Binding Protein - biosynthesis; rhoA GTP-Binding Protein - genetics; rhoA GTP-Binding Protein - physiology; Signal Transduction - drug effects; Transcription, Genetic; Uterine Contraction - drug effects; Uterine Contraction - physiology; Uterus - metabolism
• ISSN: 0013-7227
• DOI: 10.1210/en.143.3.920

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.