title: Cyclic adenosine 3'5'-monophosphate and the relaxant action of relaxin in the rat uterus in vivo.
abstract: The relationship between relaxant actions of relaxin in the uterus and changes in uterine cAMP concentrations was assessed in anaesthetized bilaterally ovariectomized nonpregnant rats. Relaxin i.v. bolus (5 micrograms kg-1) did not change cAMP concentrations but inhibited uterine contractions with rapid onset. Uterine contractions were significantly reduced by 30-70% for 60 min. Relaxin (50 micrograms kg-1) produced a short-lived (up to 5 min) and small (up to 3.2-fold) increase in cAMP concentrations plus a marked (90%) and prolonged inhibition of uterine contractions (70-90% over 60 min). Salbutamol (an agonist at beta 2-adrenoceptors, 100 and 500 micrograms kg-1) produced a similar degree and time course of inhibition of uterine contractions to that of relaxin but a more marked (19-fold) increase in cAMP concentrations. Glibenclamide, a blocker of ATP-sensitive potassium channels, which has been shown to antagonize relaxin as a uterine relaxant, did not prevent the relaxin-induced rise in cAMP concentrations. It is suggested that the uterine relaxant action of relaxin may not result from an increase in uterine cAMP concentrations.
authors.affiliation: Department of Physiological Sciences, Medical School, Manchester University, UK.
authors.forename: S J
authors.initials: SJ
authors.lastname: Downing
authors.forename: A
authors.initials: A
authors.lastname: McIlwrath
authors.forename: M
authors.initials: M
authors.lastname: Hollingsworth
mesh_terms: D000420:Albuterol / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D000242:Cyclic AMP / Q000096:biosynthesis*; D004305:Dose-Response Relationship, Drug; D005260:Female; D005905:Glyburide / Q000494:pharmacology; D010052:Ovariectomy; D015221:Potassium Channels / Q000187:drug effects / Q000502:physiology; D051381:Rats; D018343:Receptors, Adrenergic, beta-2 / Q000502:physiology; D012065:Relaxin / Q000502:physiology*; D013997:Time Factors; D014590:Uterine Contraction / Q000187:drug effects / Q000502:physiology*; D014599:Uterus / Q000378:metabolism
chemical_list: D015221:Potassium Channels; D018343:Receptors, Adrenergic, beta-2; D012065:Relaxin; D000242:Cyclic AMP; D000420:Albuterol; D005905:Glyburide