Effect of amiloride on contractility of rat cardiac muscle exposed to chronic hypercapnia and acute acidosis

Abstract
Papillary muscle preparations from rats with normal arterial oxygen and carbon dioxide tensions and from rats which had been maintained with normal oxygen tension but with hypercapnia for 28 days (FICO2=5%) were subjected to acute hypercapnia with or without amiloride, a competitive inhibitor of the Na+/H+ pump. Acclimatisation to hypercapnia reduced the slope of the line relating log tension against the extracellular pH from 0.96(SEM0.06) to 0.71(0.07) (p+/H+ exchanger is important in the protection of rat cardiac muscle against acute respiratory acidosis.