Mechanism of action of ethanol on heart contractility

Ethanol depresses heart contractility. To investigate the mechanism of the negative inotropic action of ethanol, rat ventricular strips were dissected and mounted vertically in a transparent chamber. The preparation was superfused initially with normal oxygenated Tyrode solution (32.50C) and electrically stimulated (1 Hz). After 1 hour of equilibration, contractures were elicited by exposing the muscle strips to high K+ (100 mM) solution. Studies on the influence of (Ca2+)0 on K+ contractures showed that the first rapid component of the contracture (58 mg/sec - S.E. +/- 8; n = 8) was greatly dependent upon (Ca2+)0 while the second slow component (20 mg/sec - S.E. +/- 5; n = 8) was slightly altered. The addition of ethanol (400 mg/100 ml) to high K solution abolished the fast component and reduced the amplitude of the second phase of K contractures. Similar results were obtained with verapamil (10-5 M). These results, as well as studies on the effect of the drug on 45Ca fluxes support the view that ethanol decreases the permeability of the heart cell membrane to Ca