Effects of chloride on the electrical and mechanical properties of guinea pig ventricle.

The purpose of this study was to investigate the influence of chloride on the electrical and mechanical properties of the guinea pig ventricular myocardium. Bathing media were made chloride free by substituting the relatively impermeant anion gluconate, isethionate, or sulfate. Removal of chloride increased contractility and decreased the duration of the action potential. Additional experiments explored the influence of chloride free media on electrogenic calcium influx estimated from the magnitude of the action potential in cells partially depolarized by potassium (the slow response). In the absence of chloride, transient increases occurred in the magnitude of the slow response while the positive inotropic effect was maintained. These experiments suggest that the effects of chloride free media are mediated secondarily by an enhanced calcium influx.