Pharmacology The positive inotropic effect of digitalis is due to inhibition of Na+/K+ ATPase pump in cardiac muscle cell membrane leading to: A Decreased activity of Na+/Ca++ exchanger causing decreased influx of sodium and decreased efflux of Ca++ in the sarcolemma B Decreased efflux of Na+ leading to less negative resting membrane potential and opening of voltage gated Ca++ channels on the T tubules C Increased intracellular Na+ causing increased efflux of Na+ and increased influx of Ca++ through Na+/Ca++ exchanger in the sarcolemma D Increased intracellular Na+ decreasing the activity of Ca++ pump in the sarcoplasmic reticulum 💡 Explanation The positive inotropic effect of digitalis is due to inhibition of Na+/K+ ATPase pump in cardiac muscle cell membrane leading to: ✓ Correct Answer: A. Decreased activity of Na+/Ca++ exchanger causing decreased influx of sodium and decreased efflux of Ca++ in the sarcolemma