Acidosis and Ca2+ current gating. Effect of acidosis on the voltage dependence of rabbit ICa,L activation and inactivation. The voltage-clamp protocol for inactivation is shown in the inset. The clamp protocol for activation is given in Materials and methods, and the smooth lines are best fits with Boltzmann functions. The normal pipette filling solution (no BAPTA) was used in all experiments shown in this figure. The clamp protocols were applied first in the control solution (black), then after 2 min in the acidic solutions (red). Tables S1 and S2 summarize the parameters for the curves shown in this figure. (A) Extracellular acidosis (n = 6) elicited right shifts in both activation and inactivation curves. (B) Intracellular acidosis (n = 13) shifted both curves to the left, with a larger shift in activation. (C) Combined acidosis (n = 11) shifted both curves back to the right compared with intracellular acidosis.
