Subclassification of cardiac glycoside receptors.

Abstract

It is widely accepted that cardiac glycosides are therapeutically efficient to treat heart failure. Their beneficial action may be attributed to their positive inotropic effect, even if their action on preload and afterload has to be taken into account (12). Despite of the large interest devoted to these drugs, the mechanism of their inotropic action is still a matter of controversy. In 1953, Schatzman reported that cardiac glycosides inhibit the ionic restoration of red blood cells occurring during rewarming after an incubation at low temperature which altered the physiological distribution of Na and K. This observation showed that the glycosides alter the transport of monovalent cations against their electrochemical gradient. In 1957, Skou discovered Na,K-ATPase and since, the mechanism of Na and K transport has been extensively investigated. Several physiological processes are coupled to the Na,K-pump, the identification of this coupling has been demonstrated by blockade of the pump by large doses of cardiac glycosides.