Fig. 1. Activation of Na⁺/H⁺ exchange during oocyte growth. Intracellular pH was monitored in growing oocytes using epifluorescence microscopy. (A) Each panel shows a typical replicate of a given experiment, each individual trace representing a single oocyte. Acidosis was induced in mid-growth phase (left panel) and fully grown (middle panel) oocytes using a 10-minute pulse of NH₄Cl (black bar). Note that neither population of oocytes mounts a substantial recovery from acidosis in media devoid of Na⁺ (gray bar), but resting pH is rapidly restored in fully grown oocytes following Na⁺ replacement. Insets show examplar fluorescence micrographs from each respective experiment. Scale bar: 50 µm. Where used, amiloride (1 mM) was added at t=20 minutes, and remained in the bath thereafter. Note that amiloride retards recovery from acidosis in fully grown oocytes (right panel). (B) Analysis of rate of recovery from acidosis following Na⁺ replacement. Different letters above the bars indicate significant differences P<0.01 (ANOVA). Three replicates were performed of each experiment - a total of 52, 32 and 39 oocytes, respectively.