Effect of amiloride on sodium-calcium exchange activity in rat cardiac myocytes.

The effect of amiloride on Na+/Ca2+ exchange activity and adenylate energy charge in isolated rat cardiac myocytes has been studied. Amiloride inhibits Na+/Ca2+ exchange activity in rat cardiac myocytes with an IC50 of 1.76 mM when added to the external side of the cell membrane, whereas it is a weaker inhibitor when present at the cytoplasmic side. The adenylate energy charge in rat cardiac myocytes is unaffected by amiloride.