Schematic summary of acidosis effects on I_Ca,L. Extracellular acidosis decreases peak I_Ca,L by directly blocking the channel pore and by shifting current activation toward less negative potentials. It also reduces late Ca²⁺ entry during an AP. In contrast, intracellular acidosis stimulates peak I_Ca,L by shifting activation toward more negative potentials. This stimulatory effect is blunted by the H⁺-induced rise of diastolic Ca²⁺, which promotes channel inactivation. Intracellular acidosis also enhances late Ca²⁺ entry during an AP. A mixed response of I_Ca,L occurs when pH_i and pH_o changes are imposed simultaneously.