Figure 5. Response of pH_i to potassium-induced depolarization without osmotic compensation.

A, guinea pig myocyte: response of pH_i to superfusion with hypertonic solution (generated by directly adding either 40 mm NaCl or 40 mm KCl to Tyrode solution, denoted as 40 Na and 40 K, respectively) in the absence and then in the presence of 250 μm DIDS. B, rat myocyte: response of pH_i to isotonic hyperkalaemia (80 mm) or hypertonic hyperkalaemia (80 mm), denoted by 80K(iso) and 80K, respectively. These solutions were first applied in the absence of CO₂/HCO₃⁻ (Hepes-buffered), then in CO₂/HCO₃⁻-buffered solution. C, rabbit myocytes: pooled data showing effect on pH_i of hypertonic hyperkalaemia (44.4 mm) without (n = 5) and with (n = 7) 30 μm HOE 642. The absence of full pH_i recovery after removal of hyperkalaemia was evident in all cells tested.