title: Negative inotropic effects of angiotensin II, endothelin-1 and phenylephrine in indo-1 loaded adult mouse ventricular myocytes.
abstract: Angiotensin II (Ang II). endothelin-1 (ET-1) and phenylephrine are receptor agonists that share the signal transduction acting through acceleration of phosphoinositide hydrolysis in the heart. Because the regulation of myocardial contractility induced by these receptor agonists shows a wide range of species-dependent variation among experimental animals, we carried out experiments to elucidate the mechanism of contractile regulation induced by these agents in mice which are employed currently more as transgenic models. Effects of Ang II, ET-1 and phenylephrine on cell shortening and Ca2+ transients were investigated in single ventricular myocytes loaded with indo-1/AM. Ang II (10(-8), 10(-7) M), ET-1 (10(-10), 10(-9) M) and phenylephrine (10(-6), 10(-5) M in the presence of the beta-adrenoceptor antagonist timolol) decreased the cell shortening [Ang II: 58.4+/-9.03 (n = 8), 50.3+/-11.90% (n = 6); ET-1: 48.4+/-8.27, 31.2+/-6.45% (n = 5); phenylephrine: 45.7+/-11.60, 28.7+/-5.89% (n = 5)]. By contrast, the amplitude of Ca2+ transients was not significantly influenced by these agonists. The selective protein kinase C inhibitor chelerythrine at 10(-6) M significantly inhibited the decrease in cell shortening induced by these receptor agonists. These results indicate that Ang II, ET-1 and phenylephrine elicit a negative inotropic effect with insignificant alteration of Ca2+ transients, which may be mainly mediated by activation of protein kinase C in mouse ventricular cardiomyocytes.
authors.affiliation: Department of Pharmacology, Yamagata University School of Medicine, Japan.
authors.forename: Kiyoharu
authors.initials: K
authors.lastname: Sakurai
authors.forename: Ikuo
authors.initials: I
authors.lastname: Norota
authors.forename: Hisao
authors.initials: H
authors.lastname: Tanaka
authors.forename: Isao
authors.initials: I
authors.lastname: Kubota
authors.forename: Hitonobu
authors.initials: H
authors.lastname: Tomoike
authors.forename: Masao
authors.initials: M
authors.lastname: Endo
mesh_terms: D000470:Alkaloids; D000804:Angiotensin II / Q000494:pharmacology*; D000818:Animals; D053119:Benzophenanthridines; D002118:Calcium / Q000378:metabolism*; D003864:Depression, Chemical; D019332:Endothelin-1 / Q000494:pharmacology*; D066298:In Vitro Techniques; D007211:Indoles / Q000378:metabolism*; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D009200:Myocardial Contraction / Q000187:drug effects*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D010617:Phenanthridines / Q000494:pharmacology; D010656:Phenylephrine / Q000494:pharmacology*; D011493:Protein Kinase C / Q000037:antagonists & inhibitors / Q000502:physiology
chemical_list: D000470:Alkaloids; D053119:Benzophenanthridines; D019332:Endothelin-1; D007211:Indoles; D010617:Phenanthridines; D000804:Angiotensin II; D010656:Phenylephrine; C016299:chelerythrine; D011493:Protein Kinase C; C048960:indo-1; D002118:Calcium