An endogenous Ca 2+ channel agonist, endothelin-1, does not directly activate partially purified dihydropyridine-sensitive Ca 2+ channel from cardiac muscle in a reconstituted system

• Published in: Biochemical and biophysical research communications Vol. 171; no. 3; pp. 1205 - 1210
• Main Authors: Naitoh, Toshihiko, Toyo-Oka, Teruhiko, Sugimoto, Tsuneaki
• Format: Journal Article
• Language: English
• Published: Elsevier Inc 28.09.1990
• ISSN: 0006-291X; 1090-2104
• DOI: 10.1016/0006-291X(90)90813-3

To elucidate the action of tentative endogenous Ca 2+ channel activator, endothelin (ET)-1, on a voltage-dependent Ca 2+ channel in the heart, a dihydropyridine (DHP)-binding protein was solubilized from porcine ventricular muscle, partially purified by wheat germ agglutinin-affinity chromatography and reconstituted into proteoliposomes. Ca 2+ flux into the proteoliposomes was determined using a fluorescent probe, Quin-2. The initial Ca 2+ entry rate was dose-dependently activated by either a K +-depolarization or a synthetic Ca 2+ channel agonist, Bay K8644, and inhibited by several Ca 2+ entry blockers or cadmium ions. Using the same reconstituted system, it was demonstrated that sufficient dose of ET-1 yielded no effect on the Ca 2+ channel function, indicating that the ET-1 action was not directly mediated by the voltage-dependent, DHP-sensitive Ca 2+ channel.