Mechanistic distinction between activation and inhibition of (Na++K+)-ATPase-mediated Ca2+ influx in cardiomyocytes

► Nifedipine blocks the activation of (Na++K+)-ATPase-induced 45Ca influx in myocytes. ► KB-R7943 fails to inhibit the activation of (Na++K+)-ATPase-induced 45Ca influx. ► Reverse-mode Na+/Ca2+-exchanger is a major source for the 45Ca influx induced by ouabain. ► SSA412-mediated Ca2+ influx is independent of the reverse-mode Na+/Ca2+-exchanger.