title: Differential action of a protein tyrosine kinase inhibitor, genistein, on the positive inotropic effect of endothelin-1 and norepinephrine in canine ventricular myocardium.
abstract: Experiments were carried out in isolated canine ventricular trabeculae and acetoxymethylester of indo-1-loaded single myocytes to elucidate the role of protein tyrosine kinase (PTK) in the inotropic effect of endothelin-1 (ET-1) induced by crosstalk with norepinephrine (NE). The PTK inhibitor genistein was used as a pharmacological tool. Genistein but not daidzein inhibited the positive inotropic effect and the increase in Ca(2+) transients induced by ET-1 by crosstalk with NE at low concentrations. Genistein and daidzein antagonized the negative inotropic effect and the decrease in Ca(2+) transients induced by ET-1 by crosstalk with NE at high concentrations, but genistein did not affect the antiadrenergic effect of carbachol. Genistein but not daidzein enhanced the positive inotropic effect and the increase in Ca(2+) transients induced by NE via beta-adrenoceptors, while the enhancing effect of genistein was abolished by the protein tyrosine phosphatase inhibitor vanadate. These findings indicate that genistein (1) induces a positive inotropic effect in association with an increase in Ca(2+) transients, (2) inhibits the positive inotropic effect of ET-1 induced by crosstalk with NE, and (3) enhances the positive inotropic effect of NE induced via beta-adrenoceptors by inhibition of PTK. In addition, genistein inhibits the negative inotropic effect of ET-1 induced by crosstalk with NE through a PTK-unrelated mechanism. PTK may play a crucial role in the receptor-mediated regulation of cardiac contractile function in canine ventricular myocardium.
authors.affiliation: Department of Cardiovascular Pharmacology, Yamagata University School of Medicine, 2-2-2 Iida-nishi, Yamagata 990-9585, Japan.
authors.forename: Li
authors.initials: L
authors.lastname: Chu
authors.forename: Jian-Xin
authors.initials: JX
authors.lastname: Zhang
authors.forename: Ikuo
authors.initials: I
authors.lastname: Norota
authors.forename: Masao
authors.initials: M
authors.lastname: Endoh
mesh_terms: D000818:Animals; D020013:Calcium Signaling / Q000187:drug effects; D002316:Cardiotonic Agents / Q000494:pharmacology*; D002469:Cell Separation; D004285:Dogs; D019332:Endothelin-1 / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology*; D019833:Genistein / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects*; D006352:Heart Ventricles / Q000187:drug effects; D066298:In Vitro Techniques; D007211:Indoles / Q000494:pharmacology; D009200:Myocardial Contraction / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000187:drug effects; D009638:Norepinephrine / Q000494:pharmacology*; D011505:Protein-Tyrosine Kinases / Q000037:antagonists & inhibitors*; D020239:Receptor Cross-Talk / Q000187:drug effects; D011943:Receptors, Adrenergic, beta / Q000187:drug effects
chemical_list: D002316:Cardiotonic Agents; D019332:Endothelin-1; D004791:Enzyme Inhibitors; D007211:Indoles; D011943:Receptors, Adrenergic, beta; D019833:Genistein; D011505:Protein-Tyrosine Kinases; C048960:indo-1; D009638:Norepinephrine