A comparison of the effects of ouabain, dihydroouabain and 3 alpha-methyldigitoxigenin glucoside on guinea pig left atria.

The effects of ouabain, dihydroouabain and 3 alpha-methyldigitoxigenin glucoside on force of contraction and 86Rb+-uptake were measured in contracting guinea pig left atria. Dihydroouabain and 3 alpha-methyldigitoxigenin glucoside were both about 40 times less potent than ouabain. All compounds gave approximately the same maximal increase in force of contraction. The results gave no evidence that either dihydroouabain or 3 alpha-methyldigitoxigenin glucoside has a greater therapeutic index than ouabain. All compounds showed similar effect on 86Rb+-uptake (no significant change at positive inotropic concentrations, significantly decreased 86Rb+-uptake only at toxic concentrations). These results imply that these three compounds have a similar mechanism of action.