Fig. 9.
Simulations of pHi and pHS transients for the addition of graded levels of extracellular CO2/HCO3− in 5 mM HEPES. A: ”control“ oocyte”. B: “CA II” oocyte. C: “CA IV” oocyte. The pHi transients, calculated at a depth of ∼50 μm, are represented by the red lower trajectories, and pHS, by the green upper trajectories. At the indicated time, we switched the extracellular solution from CO2/HCO3−-free “ND96” to 1) 1.5% CO2/10 mM HCO3− (left), or 2) 5% CO2/33 mM HCO3− (center), or 3) 10% CO2/66 mM HCO3− (right). The dashed black lines through the initial portions of the pHi transients for CO2 application represent the maximal rates of pHi change (negative direction) predicted by the model. The upward arrow near the pHS records represent maximal changes in pHS (positive direction).