[The effects of endothelin-1 on myocardial function].
BACKGROUND
Endothelin-1 (ET-1) has potent vasoconstrictor, growth promoting and positive inotropic properties, with increased plasma levels in heart failure (HF). With regard to the cardiac effects of ET-1, most studies have not been able to differentiate its effects on the intrinsic properties of the myocardium from the secondary effects resulting from load changes and coronary vasoconstriction. This study investigated the myocardial effects of ET-1.


METHODS
The study was performed on isolated rabbit papillary muscles (n = 9), before and after the addition of ET-1 (10 nM) to the superfusing solution (Krebs-Ringer; 1.25 nM Ca2+; 35 degrees C). One isotonic, one isometric and two afterloaded-isotonic twitches were recorded and analyzed. Only significant results (mean +/- SE, p < 0.05) are given, expressed as delta % baseline.


RESULTS
ET-1 induced an increase of AT (147 +/- 33%), dT/dtmax (154 +/- 39%) and dT/dtmin (145 +/- 38%), while the duration of the twitch did not vary significantly. In addition, after ET-1, RT at the end of the isometric twitch decreased by 19 +/- 3%, when compared with the control and to its value at the beginning of the twitch.


CONCLUSIONS
This study showed that, in addition to the well-known positive inotropic effect, ET-1 improves diastolic function by accelerating relaxation rate (dT/dtmin) and decreasing RT. These results may have important implications in the pathophysiology of HF.
Leite-Moreira
A F
AF
Serviço de Fisiologia, Faculdade de Medicina, Universidade do Porto.
Rocha-Sousa
A
A
Henriques-Coelho
T
T
Roncon-Alburqueque Júnior
R
R
Chaves
P
P
D000818:Animals; D002316:Cardiotonic Agents / Q000494:pharmacology*; D003971:Diastole / Q000187:drug effects; D019332:Endothelin-1 / Q000494:pharmacology*; D006321:Heart / Q000187:drug effects* / Q000502:physiology; D066298:In Vitro Techniques; D009129:Muscle Tonus / Q000187:drug effects; D009200:Myocardial Contraction / Q000187:drug effects; D010210:Papillary Muscles / Q000187:drug effects / Q000502:physiology; D011817:Rabbits; D013599:Systole / Q000187:drug effects
D002316:Cardiotonic Agents; D019332:Endothelin-1