Figure 5. Measuring the rate constant for intracellular CO₂ hydration, k₁.

A, upper panel: sample experiment showing acetate prepulse with and without ATZ; lower panel: amplified sections of trace showing recovery phase with and without ATZ; continuous lines are fitted using the estimated value for k₁, as described in the text and Appendix; correlation coefficient > 0.9999 (Student's paired t test). B, diagram of scheme assumed when calculating k₁. CO₂ has rapid access across sarcolemma. Hydration generates H⁺, most of which is buffered instantaneously by intrinsic buffers in the cell (B). C, histogram showing mean value of k₁ derived from experiments like that shown in A, in absence (control) and presence of 10 μM ATZ.