Importance of bicarbonate ion for intracellular pH regulation in antigen- and ionomycin-stimulated RBL-2H3 mast cells
| Autor: | Rebecca J. Lee, G G Deanin, Robert F. Stump, Charles D. Troup, Janet M. Oliver |
|---|---|
| Rok vydání: | 1992 |
| Předmět: |
Cytoplasm
Bicarbonate Intracellular pH Biophysics Biology Fluorescence Pathology and Forensic Medicine chemistry.chemical_compound Endocrinology Antigen medicine Tumor Cells Cultured Animals Secretion Mast Cells Antigens Ion transporter Ionomycin Degranulation Cell Biology Hematology Hydrogen-Ion Concentration Mast cell Fluoresceins Molecular biology Culture Media Rats Bicarbonates medicine.anatomical_structure chemistry Biochemistry Leukemia Basophilic Acute Microscopy Fluorescence Calcium |
| Zdroj: | Cytometry. 13(2) |
| ISSN: | 0196-4763 |
| Popis: | In RBL-2H3 rat basophilic leukemia cells, Ca2+ influx and secretion are activated by antigens that crosslink IgE-receptor complexes and by the Ca2+ ionophore, ionomycin. Here we report that antigen-stimulated Ca2+ influx and secretion are impaired and ionomycin-induced responses are strongly inhibited following the removal of HCO3- from the medium. These results raised the possibility that HCO3(-)-dependent pH regulation mechanisms play a role in the cascade of events leading to mast cell activation. To test this hypothesis, intracellular pH (pHi) was measured by ratio imaging microscopy in individual RBL-2H3 cells labeled with 2',7'-bis-(2-carboxyethyl)-5-(6) carboxyfluorescein (BCECF). In unstimulated cells, it was found that basal pHi in the presence of HCO3- is 7.26, significantly greater than pHi in its absence, 7.09 (P less than 10(-6]. These results, as well as evidence that pHi increases rapidly when HCO3- is added to cells initially incubated in HCO3(-)-free medium, indicate that unstimulated cells use a HCO3(-)-dependent mechanism to maintain cytoplasmic pH. Further analyses comparing unstimulated with stimulated cells showed that antigen causes a small transient acidification in medium containing HCO3- and a larger sustained acidification in HCO3(-)-depleted medium. Ionomycin is a more potent acidifying agent, stimulating a sustained acidification in complete medium and causing further acidification in HCO3(-)-free medium. These results support the hypothesis that the inhibition of antigen- and ionomycin-induced 45Ca2+ influx and secretion in cells incubated in HCO3(-)-free medium is at least partially due to the inactivation of HCO3(-)-dependent mechanisms required to maintain pH in unstimulated cells and to permit pH recovery from stimulus-induced acidification. |
| Databáze: | OpenAIRE |
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