Fig. 2.

Time course of pH_i changes in 4 phagocytosing neutrophils. Pseudocolor images of each cell are positioned near the corresponding time point. The spatially averaged pH_i of the cell is plotted, including only areas of cytoplasm above a threshold level of fluorescence intensity; areas below the cutoff (e.g., in phagosomes) are blanked. Acidification invariably occurred rapidly after productive contact with OPZ, often followed by rapid recovery (A), but sometimes not (B). In cells pretreated with 20 μM DMA to inhibit Na⁺/H⁺ antiport (C), or 100 μM Zn²⁺ to inhibit proton current (D), pH_i decreased farther and did not recover.