THE INOTROPIC EFFECT OF ENDOTHELIN-1 IS MEDIATED BY MITOCHONDRIAL REACTIVE OXYGEN SPECIES.

DE GIUSTI VC, CORREA MV, VILLA-ABRILLE MC, BELTRANO C, YEVES AM, CHIAPPE DE CINGOLANI G, CINGOLANI E, AIELLO

LIFE SCIENCES

PERGAMON-ELSEVIER SCIENCE LTD

Año: 2008 vol. 83 p. 264 - 271

0024-3205

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 (UO2−) with chemiluminescence, and ROS production and intracellular pH (pHi) with epifluorescence. The ET-1-induced positive inotropic effect (40.4 ±3.1%, n= 10, pb0.05) was associated to an increase in ROS production (105 ± 29 fluorescence units above control, n= 6, pb0.05). ET-1 also induced an increase in U O2− production that was inhibited by the NADPH oxidase blocker, apocynin, and by the blockers of mitochondrial ATP-sensitive K+ channels (mKATP), 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 μM; 8.8 ± 3.5%, n= 6), 5 hydroxydecanoic acid (500 μM; 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 (JH) 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 μM; 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