Isoproterenol-induced desensitization to the positive inotropic effect of isoproterenol in ventricular strips isolated from carp heart (Cyprinus carpio).
Whether the positive inotropic effect of isoproterenol in ventricular strips of carp heart is altered by previous exposure to the agonist was studied. Isoproterenol produced a concentration-dependent positive inotropic effect in these preparations which was competitively antagonized by propranolol. Isoproterenol dose-response curves were shifted significantly downward and to the right after previous treatment with and removal of isoproterenol. The desensitization could be demonstrated after 5 min incubation and near maximal desensitization was observed after 30 min exposure to 1000 nM isoproterenol. The responsiveness was only partially recovered after 180 min incubation in drug-free medium. Isoproterenol produces a rapidly developing desensitization to inotropic effects of the beta-adrenergic agonist. This phenomenon may be mediated by alterations in beta-adrenergic receptors, adenylate cyclase and/or the beta receptor-adenylate cyclase coupling mechanism.
Temma
K
K
Hirata
T
T
Kitazawa
T
T
Kondo
H
H
D000818:Animals; D002122:Calcium Chloride / Q000494:pharmacology; D002347:Carps; D004305:Dose-Response Relationship, Drug; D006352:Heart Ventricles / Q000187:drug effects; D066298:In Vitro Techniques; D007545:Isoproterenol / Q000494:pharmacology*; D009200:Myocardial Contraction / Q000187:drug effects*; D011433:Propranolol / Q000494:pharmacology; D016276:Ventricular Function
D011433:Propranolol; D007545:Isoproterenol; D002122:Calcium Chloride