Premium
Inhibition of capacitative calcium entry suppresses ouabain‐induced stimulation of sodium‐hydrogen exchange in rat optic nerve astrocytes
Author(s) -
Mandal Amritlal,
Shahidullah Mohammad,
Delamere Nicholas
Publication year - 2008
Publication title -
the faseb journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.709
H-Index - 277
eISSN - 1530-6860
pISSN - 0892-6638
DOI - 10.1096/fasebj.22.1_supplement.759.2
Subject(s) - ouabain , chemistry , calcium , stimulation , bapta , sodium , ammonium chloride , bicarbonate , medicine , endocrinology , biophysics , biochemistry , biology , organic chemistry
Objective: Earlier we showed that 1 μM ouabain increased capacitative calcium entry (CCE) but did not increase cell sodium1. Here we studied cytoplasmic pH recovery after an acid load in ouabain‐treated cells and tested whether pH response were linked to altered calcium entry. Methods: Ammonium chloride (20mM) was used to acid load the cells. BCECF and FURA‐2 were used to measure intracellular pH and calcium. Results: Ammonium chloride removal causes the pH i to fall abruptly, followed by gradual recovery. lμM ouabain increased the rate of pH i recovery both in the presence and in the absence of bicarbonate in the bathing medium. NHE inhibitor DMA reduced the rate of pH i recovery. Ouabain did not detectably alter cytoplasmic Ca 2+ (Ca 2+ i ) but CCE inhibitors SKF96365 and 2APB reduced both the basal and ouabain‐stimulated rates of pH i recovery. Calcium chelator BAPTA‐AM also inhibited basal and ouabain‐stimulated pH i recovery. Western blot showed presence of NHE1 but not NHE2, NHE3 or NHE4. Conclusion: Ouabain‐induced stimulation of pH i recovery was due, at least in part, to stimulation of NHE1. Although lμM ouabain failed to alter Ca 2+ i , the findings suggest the NHE response may be dependent on CCE. Funding: NIH Grant EY014069