Fig. 3. Effect of persistent hypercapnic acidosis on contractile recovery in the presence and absence of the Na⁺/H⁺ exchanger (NHE) inhibition. (A) Isolated myocytes. During hypercapnic acidosis, contractility followed a pattern similar to that of ventricular strips, reaching control values after an initial fall. In spite of abolishing pH_i restitution with the NHE inhibitor cariporide (5 µmol l^–1), the inotropic recovery was not cancelled. (B) Ventricular strips. The presence of cariporide (5 µmol l^–1) did not modify the inotropic response of the toad ventricle to acidosis. There were no statistically significant differences between control and cariporide-treated preparations. Data are means ± s.e.m. of five experiments.