Acidosis and peak Ca²⁺ current. Effect of acidosis (red) on I_Ca,L in the absence (left panels) and presence of BAPTA dialysis (right panels). Cells (rabbit) were held at −80 mV, and clamp steps were applied at CL = 5 s. (A; left) Extracellular acidosis without BAPTA dialysis (n = 6) depressed the I-V curve and shifted it to the right. (A; right) Extracellular acidosis with BAPTA dialysis (n = 13) had the same effect. (B; left) Intracellular acidosis without BAPTA dialysis (n = 14) shifted the curve to the left and slightly increased the peak. (B; right) Intracellular acidosis with BAPTA dialysis (n = 10) shifted the curve to the left and markedly increased peak I_Ca,L. (C; left) Combined acidosis without BAPTA dialysis (n = 10) had little effect on the I-V curve except inhibition at voltages positive to 0 mV. (C; right) Combined acidosis with BAPTA dialysis (n = 11) increased I_Ca,L at voltages negative to −10 mV and caused somewhat less inhibition at more positive potentials. The example signals in each panel were obtained by clamping to 0 mV.