Figure 4. Effect of acidosis on I_to in the presence of Cd²⁺ in rat myocytes.

I_Ca,L was blocked by Cd²⁺ (0.3 mM). A, decrease of I_to by acidosis. Current activated by a step from a holding potential of -80 to +10 mV. Traces in control conditions (□) and in pH 6.0 (•) are superimposed. Inset, voltage-clamp protocol (20 ms prepulse to -40 mV to inactivate I_Na not shown). B, increase of I_to by acidosis. Current activated by a step from a holding potential of -20 to +60 mV in control (□) and in acidosis (•). Inset, voltage-clamp protocol. C, effect of acidosis on steady-state activation and inactivation curves. □, control; •, acidosis; ▵, second control. The effect of acidosis was less marked than in the absence of Cd²⁺ (with nisoldipine or 0 mM Ca²⁺_o-5 mM Mg²⁺_o to block I_Ca,L).