This is a real-world medical entrance exam question, please give the true answer based on the question and selection. Topic name: Cardiovascular system, Subject name: Pharmacology
[{'content': 'Digitalis has positive ionotropic effect by the viue of its effects on \nSelect and explain. \nA. Na+K+ ATPase pump, B. Na glucose channels, C. H+ K+ ATPase pump, D. Calcium pump', 'role': 'user'}, {'content': 'Answer: A \nExplanation: Effects of digitalis on cell biochemistry: sodium pumpinhibition. It is now generally agreed that Na+-K+ adenosine triphosphatase (ATPase), a transpo enzyme derived from the sarcolemmal sodium pump, is the primary site at which digitalis exes its effects on the myocardial cell. Refer kDT 6/e p497', 'role': 'assistant'}]