When the cardiac glycoside,digitoxin,is used for heart failure,the effects include:
(I) inhibition of phosphate hydrolysis from E₂ of the (Na⁺-K⁺) -ATPase pump
(II) activation of the (Na⁺-K⁺) -ATPase pump
(III) increase in intracellular Na⁺ concentration
(IV) increase in Ca²⁺ concentration in the sarcoplasmic reticulum

Question

Quizplus · Accepted Answer

Digitoxin inhibits phosphate hydrolysis from the (Na+K+)-ATPase pump, leading to an increase in intracellular sodium and calcium concentrations. This increase in calcium concentration in the sarcoplasmic reticulum ultimately leads to increased contractility of the heart muscle. Therefore, choices I and II are both incorrect. Choice III is correct, as digitoxin increases intracellular Na+ concentration. Finally, choice IV is also correct, as digitoxin increases Ca2+ concentration in the sarcoplasmic reticulum. Therefore, the best option is B, which includes choices I, III, and IV.

When the Cardiac Glycoside,digitoxin,is Used for Heart Failure,the Effects Include