The relationship of the sugar moieties of the cardiac glycosides to their toxicity on the intact embryonic chick heart.

A series of 19 cardiac glycosides has been tested upon the heart of the intact 72 hr. embryo chick, both by topical application and by injection into the yolk sac. Approximately half were active and half inactive by both methods in causing cardiac arrest. All of the inactive compounds contained glucose or l-arabinose, terminally in the sugar moiety. Ouabain, which contains rhamnose, was inactive by topical application but active after yolk sac injection. The results suggest that glucose and certain sugars structurally related to it, may influence the transport of glycosides across certain cell membranes.