Figure 1.

C. elegans AMsh glia buffer intracellular pH via HCO₃⁻ transport. A, Bright-field image of C. elegans immobilized on a glass slide. Dashed arrows indicate the direction of the cuts that were made with a glass micropipette before pHlourin pH imaging experiments. B, Fluorescent image of the same animal as in A, showing the pHlourin-mediated fluorescence in an AMsh cell. Scale bars, A, B: 50 μm. C, Representative trace of pHlourin fluorescence in AMsh glia before and after perfusion with a solution containing 20 mm HCO₃⁻. The intracellular pH of glia was alkalized following the perfusion with HCO₃⁻. Data from this trace were used in the analysis shown in Figure 2C. D, Average resting pH of AMsh cells in either the absence (7.13 ± 0.03, n = 4 cells) or presence (7.24 ± 0.02, n = 3 cells) of HCO₃⁻, as determined via nigericin calibration. E, F, Representative traces from NH₄Cl acid pulse experiments in AMsh glia in the absence (E) and presence (F) of HCO₃⁻. (a), (b), and (c) indicate the changes of intracellular pH associated with addition (a) and removal (b) of NH₄Cl, and the recovery from acid load (c). G, The extent of acidification (Acid, left bars) upon removal of NH₄Cl in the AMsh glia cytosol is higher in HEPES buffer alone (ΔF/F = absolute change of 0.51 ± 0.04, n = 18 cells) compared with experiments done in the presence of HCO₃⁻ (ΔF/F = 0.35 ± 0.05, n = 18 cells). However, the extent of alkalization (Alk, middle bars) upon NH₄Cl application was similar in HEPES buffer alone (ΔF/F = 0.36 ± 0.07, n = 18 cells) and 20 mm HCO₃⁻ (ΔF/F = 0.47 ± 0.07, n = 18 cells). The rate of recovery from acid load (Acid recovery, right bars) is significantly higher in the presence of 20 mm HCO₃⁻ (ΔF/F/s = 7.68 × 10⁻⁴ ± 5.92 × 10⁻⁵) compared with HEPES buffer alone (ΔF/F/s = 2.40 × 10⁻⁴ ± 4.31 × 10⁻⁵). Data are mean ± SEM. *p < 0.05 (Student's t test). ***p < 0.0001 (Student's t test).