Chronotropic responses to ethanol of mouse atrial and ventricular myocardial cells in culture.

Some single myocardial cells cultured from the neonatal mouse atrium and ventricle, which beat spontaneously, stopped contracting dose-dependently with the addition of ethanol to the culture medium. The cells of the atrium were arrested more easily than those of the ventricle. The myocardial cells which continued beating in the ethanol medium showed chronotropic responses in a dose-dependent manner. The beat rate of both atrial and ventricular cells changed very little on the addition of a low concentration of ethanol (12.5 mM). Atrial cells showed negative chronotropic responses to high concentrations of ethanol (50 and 200 mM), while ventricular cells showed transient positive responses. Addition of acetaldehyde (100 microM) slowed the beating of atrial cells severely and that of ventricular cells moderately, but failed to arrest either type of cell. The addition of hyperosmolar medium containing 200 mM sucrose caused almost no chronotropic effect on atrial cells but a strong negative one on ventricular cells, and arrested very few of either type of cell. The transient positive chronotropic responses of ventricular cells to ethanol seemed unrelated to either acetaldehyde contained in the ethanol medium or the hyperosmolarity of the ethanol medium.