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Effect of oxytocin receptor blockade on rat myometrial responsiveness to prostaglandin f(2)(alpha). 2000

T Engstrøm, and P Bratholm, and N J Christensen, and H Vilhardt
Department of Internal Medicine and Endocrinology, Herlev Hospital, University of Copenhagen, Denmark. engstrom@mfi.ku.dk

In the present study we have shown that the genetic expression of prostaglandin (PG)F(2alpha) receptor (R) and cyclooxygenase (COX)-2 increases in laboring rat myometrium. This finding was associated with a relatively weak contractile in vitro response (E:(max)) of isolated uterine strips when challenged with PGF(2alpha). Five days postpartum PGF(2alpha)-R mRNA values exceeded those during labor while COX-2 mRNA was reduced to preparturient values. Maximal contractility of isolated strips stimulated with PGF(2alpha) at this time was enhanced and E:C(50) decreased. Oxytocin treatment of estrogen-primed nonpregnant rats down-regulated uterine contractile responsiveness to PGF(2alpha), leaving mRNA values for this receptor unchanged, whereas oxytocin receptor blockade with atosiban (an oxytocin receptor antagonist) left E:(max) unaltered. In contrast, atosiban treatment of pregnant rats resulted in a 2.5-fold increase in E:(max) and a considerably reduced EC(50) during labor when compared to untreated delivering rats. The increased contractile ability was associated with a threefold increase in PGF(2alpha)-R mRNA production, indicating that the regulation by atosiban of the PGF(2alpha)-induced response is exerted at the genetic level. Based on the present data we suggest that 1) PGF(2alpha)-R stimulation may not primarily exert a contracting role in the normally delivering myometrium, and 2) the presence of the PGF(2alpha)-R system in rat myometrium may explain the apparent functional redundancy of the oxytocinergic system during the process of birth in animals lacking oxytocin or where the oxytocin receptor is blocked. In this context PGF(2alpha) receptor stimulation may, in the absence of oxytocin receptor stimulation, exert the contractile forces needed for proper propulsion of the fetus.

UI MeSH Term Description Entries
D007527 Isoenzymes Structurally related forms of an enzyme. Each isoenzyme has the same mechanism and classification, but differs in its chemical, physical, or immunological characteristics. Alloenzyme,Allozyme,Isoenzyme,Isozyme,Isozymes,Alloenzymes,Allozymes
D009215 Myometrium The smooth muscle coat of the uterus, which forms the main mass of the organ. Uterine Muscle,Muscle, Uterine,Muscles, Uterine,Uterine Muscles
D010120 Oxytocics Drugs that stimulate contraction of the myometrium. They are used to induce LABOR, OBSTETRIC at term, to prevent or control postpartum or postabortion hemorrhage, and to assess fetal status in high risk pregnancies. They may also be used alone or with other drugs to induce abortions (ABORTIFACIENTS). Oxytocics used clinically include the neurohypophyseal hormone OXYTOCIN and certain prostaglandins and ergot alkaloids. (From AMA Drug Evaluations, 1994, p1157) Oxytocic,Oxytocic Agent,Oxytocic Drug,Uterine Stimulant,Uterine Stimulants,Oxytocic Agents,Oxytocic Drugs,Oxytocic Effect,Oxytocic Effects,Agent, Oxytocic,Agents, Oxytocic,Drug, Oxytocic,Drugs, Oxytocic,Effect, Oxytocic,Effects, Oxytocic,Stimulant, Uterine,Stimulants, Uterine
D011451 Prostaglandin-Endoperoxide Synthases Enzyme complexes that catalyze the formation of PROSTAGLANDINS from the appropriate unsaturated FATTY ACIDS, molecular OXYGEN, and a reduced acceptor. Fatty Acid Cyclo-Oxygenase,PGH Synthase,Prostaglandin H Synthase,Prostaglandin Synthase,Prostaglandin-Endoperoxide Synthase,Arachidonic Acid Cyclooxygenase,Cyclo-Oxygenase,Cyclooxygenase,Cyclooxygenases,Hydroperoxide Cyclase,PGH2 Synthetase,Prostaglandin Cyclo-Oxygenase,Prostaglandin Cyclooxygenase,Prostaglandin Endoperoxide Synthetase,Prostaglandin G-H Synthase,Prostaglandin H2 Synthetase,Prostaglandin Synthetase,Cyclase, Hydroperoxide,Cyclo Oxygenase,Cyclo-Oxygenase, Fatty Acid,Cyclo-Oxygenase, Prostaglandin,Cyclooxygenase, Arachidonic Acid,Cyclooxygenase, Prostaglandin,Endoperoxide Synthetase, Prostaglandin,Fatty Acid Cyclo Oxygenase,G-H Synthase, Prostaglandin,Prostaglandin Cyclo Oxygenase,Prostaglandin Endoperoxide Synthases,Prostaglandin G H Synthase,Synthase, PGH,Synthase, Prostaglandin,Synthase, Prostaglandin G-H,Synthase, Prostaglandin H,Synthase, Prostaglandin-Endoperoxide,Synthases, Prostaglandin-Endoperoxide,Synthetase, PGH2,Synthetase, Prostaglandin,Synthetase, Prostaglandin Endoperoxide,Synthetase, Prostaglandin H2
D005260 Female Females
D000818 Animals Unicellular or multicellular, heterotrophic organisms, that have sensation and the power of voluntary movement. Under the older five kingdom paradigm, Animalia was one of the kingdoms. Under the modern three domain model, Animalia represents one of the many groups in the domain EUKARYOTA. Animal,Metazoa,Animalia
D012333 RNA, Messenger RNA sequences that serve as templates for protein synthesis. Bacterial mRNAs are generally primary transcripts in that they do not require post-transcriptional processing. Eukaryotic mRNA is synthesized in the nucleus and must be exported to the cytoplasm for translation. Most eukaryotic mRNAs have a sequence of polyadenylic acid at the 3' end, referred to as the poly(A) tail. The function of this tail is not known for certain, but it may play a role in the export of mature mRNA from the nucleus as well as in helping stabilize some mRNA molecules by retarding their degradation in the cytoplasm. Messenger RNA,Messenger RNA, Polyadenylated,Poly(A) Tail,Poly(A)+ RNA,Poly(A)+ mRNA,RNA, Messenger, Polyadenylated,RNA, Polyadenylated,mRNA,mRNA, Non-Polyadenylated,mRNA, Polyadenylated,Non-Polyadenylated mRNA,Poly(A) RNA,Polyadenylated mRNA,Non Polyadenylated mRNA,Polyadenylated Messenger RNA,Polyadenylated RNA,RNA, Polyadenylated Messenger,mRNA, Non Polyadenylated
D014590 Uterine Contraction Contraction of the UTERINE MUSCLE. Myometrial Contraction,Contraction, Myometrial,Contraction, Uterine,Contractions, Myometrial,Contractions, Uterine,Myometrial Contractions,Uterine Contractions
D014668 Vasotocin A nonapeptide that contains the ring of OXYTOCIN and the side chain of ARG-VASOPRESSIN with the latter determining the specific recognition of hormone receptors. Vasotocin is the non-mammalian vasopressin-like hormone or antidiuretic hormone regulating water and salt metabolism. 3-Isoleucyl Vasopressin,Arginine Oxytocin,Arginine Vasotocin,Argiprestocin,Vasopressin, Isoleucyl,Vasopressin, Non-Mammalian,(8-Arginine)Oxytocin,Argiprestocine,3 Isoleucyl Vasopressin,Isoleucyl Vasopressin,Non-Mammalian Vasopressin,Oxytocin, Arginine,Vasopressin, 3-Isoleucyl,Vasopressin, Non Mammalian,Vasotocin, Arginine
D015149 Tocolytic Agents Drugs that prevent preterm labor and immature birth by suppressing uterine contractions (TOCOLYSIS). Agents used to delay premature uterine activity include magnesium sulfate, beta-mimetics, oxytocin antagonists, calcium channel inhibitors, and adrenergic beta-receptor agonists. The use of intravenous alcohol as a tocolytic is now obsolete. Tocolytic,Tocolytic Agent,Tocolytic Effect,Tocolytic Effects,Tocolytics,Agent, Tocolytic,Agents, Tocolytic,Effect, Tocolytic,Effects, Tocolytic

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