Fig. 1. Biphasic inotropic effect of hypercapnic acidosis on toad ventricle. (A) Continuous recording of developed tension (DT) and maximal rate of rise of tension (+dT/dt) during isometric contraction. Hypercapnia produced an abrupt decrease in contractility followed by recovery that exceeded control values. (B) Overall results of the effect of acidosis on DT. Data are means ± s.e.m. (N=49). *P<0.05 with respect to values before hypercapnia.