title: The positive inotropic effect of endothelin-1 is mediated by mitochondrial reactive oxygen species.
abstract: We have previously demonstrated the participation of reactive oxygen species (ROS) in the positive inotropic effect of a physiological concentration of Angiotensin II (Ang II, 1 nM). The objective of the present work was to evaluate the role and source of ROS generation in the positive inotropic effect produced by an equipotent concentration of endothelin-1 (ET-1, 0.4 nM). Isolated cat ventricular myocytes were used to measure sarcomere shortening with a video-camera, superoxide anion (()O(2)(-)) with chemiluminescence, and ROS production and intracellular pH (pH(i)) with epifluorescence. The ET-1-induced positive inotropic effect (40.4+/-3.1%, n=10, p<0.05) was associated to an increase in ROS production (105+/-29 fluorescence units above control, n=6, p<0.05). ET-1 also induced an increase in ()O(2)(-) production that was inhibited by the NADPH oxidase blocker, apocynin, and by the blockers of mitochondrial ATP-sensitive K(+) channels (mK(ATP)), glibenclamide and 5 hydroxydecanoic acid. The ET-1-induced positive inotropic effect was inhibited by apocynin (0.3 mM; 6.3+/-6.6%, n=13), glibenclamide (50 microM; 8.8+/-3.5%, n=6), 5 hydroxydecanoic acid (500 microM; 14.1+/-8.1, n=9), and by scavenging ROS with MPG (2 mM; 0.92+/-5.6%, n=8). ET-1 enhanced proton efflux (J(H)) carried by the Na(+)/H(+) exchanger (NHE) after an acid load, effect that was blocked by MPG. Consistently, the ET-induced positive inotropic effect was also inhibited by the NHE selective blocker HOE642 (5 microM; 9.37+/-6.07%, n=7). The data show that the effect of a concentration of ET-1 that induces an increase in contractility of about 40% is totally mediated by an intracellular pathway triggered by mitochondrial ROS formation and stimulation of the NHE.
authors.affiliation: Centro de Investigaciones Cardiovasculares, Facultad de Ciencias Médicas, Universidad Nacional de La Plata, La Plata, Buenos Aires, Argentina.
authors.forename: V C
authors.initials: VC
authors.lastname: De Giusti
authors.forename: M V
authors.initials: MV
authors.lastname: Correa
authors.forename: M C
authors.initials: MC
authors.lastname: Villa-Abrille
authors.forename: C
authors.initials: C
authors.lastname: Beltrano
authors.forename: A M
authors.initials: AM
authors.lastname: Yeves
authors.forename: G E Chiappe
authors.initials: GE
authors.lastname: de Cingolani
authors.forename: H E
authors.initials: HE
authors.lastname: Cingolani
authors.forename: E A
authors.initials: EA
authors.lastname: Aiello
mesh_terms: D000804:Angiotensin II / Q000037:antagonists & inhibitors / Q000494:pharmacology; D000818:Animals; D002316:Cardiotonic Agents / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D002415:Cats; D002478:Cells, Cultured; D004305:Dose-Response Relationship, Drug; D019332:Endothelin-1 / Q000037:antagonists & inhibitors / Q000494:pharmacology*; D004791:Enzyme Inhibitors / Q000494:pharmacology; D016166:Free Radical Scavengers / Q000494:pharmacology; D005998:Glycine / Q000031:analogs & derivatives / Q000494:pharmacology; D006352:Heart Ventricles / Q000166:cytology / Q000378:metabolism; D008929:Mitochondria, Heart / Q000378:metabolism*; D009200:Myocardial Contraction / Q000187:drug effects; D032383:Myocytes, Cardiac / Q000166:cytology / Q000378:metabolism*; D019255:NADPH Oxidases / Q000037:antagonists & inhibitors / Q000378:metabolism; D026902:Potassium Channel Blockers / Q000494:pharmacology; D015221:Potassium Channels / Q000378:metabolism; D012518:Sarcomeres / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers / Q000037:antagonists & inhibitors / Q000378:metabolism; D013438:Sulfhydryl Compounds / Q000494:pharmacology; D013481:Superoxides / Q000037:antagonists & inhibitors / Q000378:metabolism*; D014662:Vasoconstrictor Agents / Q000037:antagonists & inhibitors / Q000494:pharmacology
chemical_list: D002316:Cardiotonic Agents; D019332:Endothelin-1; D004791:Enzyme Inhibitors; D016166:Free Radical Scavengers; C110658:N-(2-mercaptoproprionyl)-glycine; D026902:Potassium Channel Blockers; D015221:Potassium Channels; D017923:Sodium-Hydrogen Exchangers; D013438:Sulfhydryl Compounds; D014662:Vasoconstrictor Agents; D013481:Superoxides; D000804:Angiotensin II; D019255:NADPH Oxidases; D005998:Glycine