Figure 4. Temperature dependence of Na⁺−H⁺ exchange.

A, following an acid load (induced by 15 mm NH₄Cl removal) in Hepes-buffered conditions, pH_i recovery was monitored, first at 37°C and then again at 27°C. Extracellular pH was 7.4 throughout. B, acid-equivalent efflux (mean ±s.e.m.), pooled from experiments similar to that shown in A, plotted as a function of pH_i at both 27°C (•) and 37°C (○). Numbers beside symbols denote the number of observations. C, apparent Q₁₀ of Na⁺−H⁺ exchange, calculated as Q₁₀= (acid-equivalent efflux at 37°C)/(acid-equivalent efflux at 27°C) over the pH_i range shown in A.