title: Activation of protein kinase C is required for oxytocin-induced contractility in human pregnant myometrium.
abstract: Intracellular mediators regulating the initiation of parturition are not fully understood. This study was designed to determine the possible mechanism of oxytocin-induced uterine contractility during labour. In-vitro isometric contraction studies were performed with longitudinal strips of human pregnant myometrium in the presence and absence of the protein kinase C inhibitors, staurosporine and RO 31-8220, and the tyrosine kinase inhibitor, genistein. Phospholipase D activity was measured by employing the transphosphatidylation reaction. Staurosporine significantly reduced oxytocin-stimulated contractile activity with mean activity reduced by > 50% following the addition of 10(-6) M staurosporine (P < 0.01), while addition of 10(-5) M resulted in a measured mean contractile activity of approximately 10% of the control (P < 0.001, n = 5). Similarly, uterine activity was minimal with oxytocin application following incubation with RO 31-8220, mean contractile activity being reduced by approximately 40% by the addition of 10(-7) M RO 31-8220 (P < 0.05) and by approximately 87% by the addition of either 10(-6) or 10(-5) M (P < 0.01, n = 3). Conversely, addition of genistein (10(-7) and 10(-6) M) had little effect on oxytocin-induced contractions, although at a higher concentration (10(-5) M) a significant reduction in oxytocin-induced contractile activity was observed (P < 0.01). Oxytocin evoked phospholipase D activation in a concentration- and time-dependent manner in cultured human pregnant myometrial cells (n = 4). These results indicate that activation of protein kinase C and tyrosine kinase are involved in the regulation of oxytocin-mediated myometrial contractile activity and that a coupled phospholipase D/phosphatidate phosphohydrolase pathway may play a role in the sustained stimulation of myometrial activity during labour.
authors.affiliation: Department of Obstetrics and Gynaecology, University College London Medical School, UK.
authors.forename: J J
authors.initials: JJ
authors.lastname: Morrison
authors.forename: S R
authors.initials: SR
authors.lastname: Dearn
authors.forename: S K
authors.initials: SK
authors.lastname: Smith
authors.forename: A
authors.initials: A
authors.lastname: Ahmed
mesh_terms: D000328:Adult; D004789:Enzyme Activation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005260:Female; D019833:Genistein; D006801:Humans; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D007529:Isoflavones / Q000494:pharmacology; D009215:Myometrium / Q000187:drug effects*; D010121:Oxytocin / Q000627:therapeutic use*; D010739:Phospholipase D / Q000378:metabolism; D011247:Pregnancy / Q000502:physiology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000378:metabolism*; D011505:Protein-Tyrosine Kinases / Q000502:physiology; D019311:Staurosporine / Q000494:pharmacology; D014590:Uterine Contraction / Q000502:physiology*
chemical_list: D004791:Enzyme Inhibitors; D007211:Indoles; D007529:Isoflavones; D010121:Oxytocin; D019833:Genistein; D011505:Protein-Tyrosine Kinases; D011493:Protein Kinase C; D010739:Phospholipase D; D019311:Staurosporine; C064758:Ro 31-8220