Figure 5. Interaction of acidosis and Cd²⁺ in rat myocytes.

Concentration dependence of the effect of Cd²⁺ on the V_½ of activation (open symbols) or inactivation (filled symbols) in control (squares), acidosis (circles) and second control (triangles). With increasing Cd²⁺ concentration, the V_½ of both activation and inactivation was shifted to more positive potentials. The effect of acidosis consisted of a further shift of V_½ to a more positive value but the magnitude of this additional shift decreased with increasing Cd²⁺ concentration. At 5 mM Cd²⁺ acidosis failed to induce a further shift. The values at 0 mM Cd²⁺ were obtained with nisoldipine as the I_Ca,L blocker. Different Cd²⁺ concentrations were applied in different groups of cells; n varied between 3 and 8. Data points were fitted by eye (continuous lines).