Fig. 10.

Effects of intracellular acidosis on AP and I_to in PM myocytes. A: example experiment showing the effect of intracellular acidosis (80.0 mM acetate) to prolong APD with little effect on phase 1 repolarization. CL = 2 s. Inset: expanded view of phase 1 repolarization. B, a: summarized APD₉₀ results for low pH_i in PM myocytes at CL = 2 s (n = 8; **P < 0.01, paired). b: % change in APD₉₀ relative to control after 2 min of low pH_i in Epi (n = 11; same results as Fig. 2D) and PM (n = 8; **P < 0.01, unpaired) myocytes. C: low pH_i in PM myocytes (n = 8) depressed I_to at nearly all voltages. CL = 5 s. **P < 0.01, paired. Control I-V curve from Epi myocytes shows same data as Fig. 6B. D: summary of results for I_to in Epi (n = 9) and PM (n = 8) myocytes at +50 mV and % change relative to control. CL = 5 s. ^##P < 0.01, unpaired, comparison of control I_to amplitude in Epi and PM myocytes; **P < 0.01, paired, control vs. acidosis.