title: Enhanced contractile response to thrombin in the pregnant rat myometrium.
abstract: Thrombin causes various cellular events by activating protease-activated receptors (PARs). Here, we showed, for the first time, that thrombin induced myometrial contraction. To determine the mechanism of thrombin-induced myometrial contraction, we simultaneously measured intracellular Ca(2+) concentration ([Ca(2+)](i)) and tension of fura-PE3-loaded rat myometrium using front-surface fluorimetry. The expression of thrombin receptor mRNA in the rat myometrium were determined by reverse transcription-polymerase chain reaction analysis (RT - PCR analysis). Thrombin (0.01 - 3 u ml(-1)) caused dose-dependent increase in [Ca(2+)](i) and tension in the rat myometrium, and this effect was greatly enhanced in the pregnant myometrium. PAR1-activating peptide mimicked the effects of thrombin. In Ca(2+)-free PSS, thrombin induced no increase in [Ca(2+)](i) and tension in the pregnant myometrium. Both diltiazem (10 microM) and SK-F 96365 (10 microM) significantly inhibited the thrombin-induced elevations of [Ca(2+)](i) and tension, and their effects were additive. RT - PCR analysis revealed an approximately 10 fold increase in the level of thrombin receptor mRNA in the pregnant myometrium compared to that obtained in the non-pregnant myometrium. In conclusion, the contractile response to thrombin was greatly enhanced in the pregnant myometrium, mainly due to the up-regulation of thrombin receptor. We propose that initiation of a post-parturitional myometrial contraction is one of the most important physiological roles of thrombin receptor.
authors.affiliation: Department of Molecular Cardiology, Research Institute of Angiocardiology, Graduate School of Medical Sciences, Kyushu University, Fukuoka, 812-8582, Japan.
authors.forename: Y
authors.initials: Y
authors.lastname: Shintani
authors.forename: K
authors.initials: K
authors.lastname: Hirano
authors.forename: J
authors.initials: J
authors.lastname: Nishimura
authors.forename: H
authors.initials: H
authors.lastname: Nakano
authors.forename: H
authors.initials: H
authors.lastname: Kanaide
mesh_terms: D000818:Animals; D002118:Calcium / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005260:Female; D005470:Fluorometry; D005786:Gene Expression Regulation / Q000187:drug effects; D005865:Gestational Age; D006801:Humans; D066298:In Vitro Techniques; D009119:Muscle Contraction / Q000187:drug effects*; D009215:Myometrium / Q000187:drug effects* / Q000378:metabolism / Q000502:physiology; D010446:Peptide Fragments / Q000494:pharmacology; D010664:Phenylmethylsulfonyl Fluoride / Q000031:analogs & derivatives* / Q000494:pharmacology; D011188:Potassium / Q000494:pharmacology; D011247:Pregnancy; D011480:Protease Inhibitors / Q000494:pharmacology; D012333:RNA, Messenger / Q000187:drug effects / Q000235:genetics / Q000378:metabolism; D051381:Rats; D011921:Rats, Inbred WKY; D044463:Receptor, PAR-1; D018179:Receptors, Thrombin / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013917:Thrombin / Q000494:pharmacology*; D013997:Time Factors
chemical_list: D010446:Peptide Fragments; D011480:Protease Inhibitors; D012333:RNA, Messenger; D044463:Receptor, PAR-1; D018179:Receptors, Thrombin; C086309:thrombin receptor peptide SFLLRNP; D010664:Phenylmethylsulfonyl Fluoride; C027226:(4-amidinophenyl)methanesulfonyl fluoride; D013917:Thrombin; D011188:Potassium; D002118:Calcium