title: Effects of endothelins, Bay K 8644 and other oxytocics in non-pregnant and late pregnant rat isolated uterus.
abstract: Endothelins 1, 2 and 3 (ET-1, ET-2 and ET-3; 1-30 nM) caused long-lasting concentration-dependent tonic contractions of uterine strips from non-pregnant rats. The potency of ET-1 (EC50 7 nM) was similar to that of angiotensin II (AII) and greater than that of ET-2 or ET-3 (EC50S greater than or equal to 10 nM), bradykinin, Bay K 8644, oxytocin (OT), 5-hydroxytryptamine, prostaglandin F2 alpha (PGF2 alpha) or acetylcholine. Strips from 21-day pregnant rats were 2- to 3-fold more sensitive to ET-1, AII, OT and PGF2 alpha and 200-fold more sensitive to Bay K 8644 than non-pregnant preparations. The development of tonic responses to ET-1 (30 nM) and of phasic-rhythmic ones to Bay K 8644 (300 nM) was fully prevented in strips from non-pregnant rats bathed in Ca2(+)-free medium, but stepwise reintroduction of Ca2+ (0.03-3 mM) to the solution allowed the manifestation of contractions in response to both agonists. Responses to ET-1 required less Ca2+ than those to Bay K 8644. Strips challenged with ET-1 while in Ca2(+)-free medium developed greater contractions upon reintroduction of Ca2+ than preparations stimulated with the peptide in normal medium. The reverse occurred with Bay K 8644-induced contractions. Nicardipine (10 nM) abolished the responses of strips from non-pregnant rats to Bay K 8644 (300 nM), but only attenuated ET-1-induced (30 nM) contraction.(ABSTRACT TRUNCATED AT 250 WORDS)
authors.affiliation: Department of Pharmacology (CCB), Universidade Federal de Santa Catarina, Florianópolis, SC, Brazil.
authors.forename: J B
authors.initials: JB
authors.lastname: Calixto
authors.forename: G A
authors.initials: GA
authors.lastname: Rae
mesh_terms: D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology*; D000818:Animals; D002118:Calcium / Q000378:metabolism / Q000494:pharmacology; D015237:Dinoprost / Q000494:pharmacology; D016232:Endothelins / Q000494:pharmacology*; D005260:Female; D066298:In Vitro Techniques; D009529:Nicardipine / Q000494:pharmacology; D010120:Oxytocics / Q000494:pharmacology*; D011247:Pregnancy; D011270:Pregnancy, Animal / Q000187:drug effects*; D051381:Rats; D011919:Rats, Inbred Strains; D012701:Serotonin / Q000494:pharmacology; D014590:Uterine Contraction / Q000187:drug effects; D014599:Uterus / Q000187:drug effects*
chemical_list: D016232:Endothelins; D010120:Oxytocics; D012701:Serotonin; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D015237:Dinoprost; D009529:Nicardipine; D002118:Calcium