Inotropic effect of PGE1 and PGE2 on isolated rat atria. Influence of adrenergic mechanisms.
The effects of a wide range of PGE1 and PGE2 concentrations on the isometric developed tension of isolated rat atria beating spontaneously or paced at a fixed rate, were explored. PGE1 only produced a negative inotropic effect (NIE), whereas PGE2 elicited a biphasic inotropic action; negative at low concentrations and positive (PIE) at higher ones. Phenoxybenzamine and phentolamine failed to modify either the NIE or the PIE, but subthreshold exogenous norepinephrine abolished the NIE, suggesting a presynaptic inhibitory effect of PGEs on the adrenergic neurotransmitter release. Auricles pretreated with subthreshold norepinephrine react with a PIE to PGE1, but not to PGE2. On the contrary in the presence of subthreshold methoxamine the PIE of PGE2 was increased whereas the action of PGE1 was not modified.
D000316:Adrenergic alpha-Agonists / Q000494:pharmacology*; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D006325:Heart Atria / Q000187:drug effects; D066298:In Vitro Techniques; D008297:Male; D008729:Methoxamine / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects*; D009638:Norepinephrine / Q000494:pharmacology; D011458:Prostaglandins E / Q000494:pharmacology*; D051381:Rats
D000316:Adrenergic alpha-Agonists; D000318:Adrenergic beta-Agonists; D011458:Prostaglandins E; D008729:Methoxamine; D009638:Norepinephrine