THE KINETICS OF CARDIAC GLYCOSIDE INHIBITION OF POTASSIUM TRANSPORT IN HUMAN ERYTHROCYTES

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Abstract
The pres-ent study represents an attempt to interpret the action of cardiac glyco-sides on red cells in kinetic terms. The following conclusions emerge. First, it is possible to account for the action of the glycosides on K transport on the basis of competition of glycoside and K for a substrate which is limited in amount, possibly a site on the cell surface. Second, the kinetics of this competition permit an estimate of the maximum number of sites, or substrate molecules, per cell and of the number of times each site passes its K onward for transmission into the cell. The affinity of the glycoside for the site has been expressed in terms of an association constant, and such constants have been determined for nine glycosides and aglycones. From the relationship of these constants to the mean lethal glycoside dose for the cat it appears that the action of the drug on red cells is in many respects similar to its action on the heart of the living animal.