title: Role of physiological HCO3-buffer on intracellular pH and histamine release in rat peritoneal mast cells.
abstract: The purpose of this study was to examine how intracellular pH (pHi) regulation and histamine release are affected by HCO3- in rat peritoneal mast cells. The pHi was measured using the pH-sensitive dye 2', 7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF). We observed a pHi of 6.88+/-0.012 (n=24) in resting mast cells exposed to a HEPES buffer (pH 7.4), but a sustained drop of 0.21 pH units to 6.67+/-0.015 (n=23) when we exposed the mast cells to a HEPES/HCO3- buffer equilibrated at all time with 5% CO2 (pH 7.4). This fall in pHi is inhibited by the carbonic anhydrase inhibitor dichlorphenamide and is Na+-independent, indicating the involvement of Na+-independent Cl-/HCO3- exchange activity. Furthermore removal of external Cl- in the presence but not in the absence of HCO3- reversed the Cl-/HCO3- exchange and induced an alkaline load. The recovery from this alkaline load was dependent on external Cl- but independent of Na+. Both the alkalinization and the recovery were inhibited by the anion transport inhibitor 4, 4'-diisothiocyanatostilbene-2,2'-disulphonic acid (DIDS). In addition, 36Cl- uptake measurements confirm the presence of a Cl-/HCO3- exchanger. Histamine release stimulated by antigen and compound 48/80 was substantially reduced in the presence of HEPES/ HCO3- buffer (pHo 7.4, pHi 6.66). Histamine release was increased, however, when pHi was clamped to 6.66 in HCO3--free media (pHo 6.9). We conclude that: (1) Na+-independent Cl-/HCO3- exchange determines steady-state pHi in rat peritoneal mast cells; and (2) the reduction in histamine release observed in the presence of HCO3- is not due to its effect on pHi per se, but rather on other changes in ion transport.
authors.affiliation: Department of Pharmacology, Institute of Medical Biology, The Medical School, Odense University, Winsloewparken 19, DK-5000 Odense C, Denmark.
authors.forename: T B
authors.initials: TB
authors.lastname: Jensen
authors.forename: U G
authors.initials: UG
authors.lastname: Friis
authors.forename: T
authors.initials: T
authors.lastname: Johansen
mesh_terms: D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000584:Amiloride / Q000031:analogs & derivatives / Q000494:pharmacology; D000818:Animals; D000941:Antigens / Q000276:immunology; D017920:Antiporters / Q000378:metabolism; D001639:Bicarbonates / Q000378:metabolism*; D001692:Biological Transport / Q000187:drug effects; D002021:Buffers; D002257:Carbonic Anhydrase Inhibitors / Q000494:pharmacology; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides / Q000378:metabolism; D004005:Dichlorphenamide / Q000494:pharmacology; D006632:Histamine / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007424:Intracellular Fluid / Q000187:drug effects / Q000378:metabolism*; D008297:Male; D008407:Mast Cells / Q000187:drug effects / Q000276:immunology / Q000378:metabolism*; D010529:Peritoneal Cavity / Q000166:cytology*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000378:metabolism; D003189:p-Methoxy-N-methylphenethylamine / Q000494:pharmacology
chemical_list: D000941:Antigens; D017920:Antiporters; D001639:Bicarbonates; D002021:Buffers; D002257:Carbonic Anhydrase Inhibitors; D027963:Chloride-Bicarbonate Antiporters; D002712:Chlorides; C057360:5-(N,N-hexamethylene)amiloride; D003189:p-Methoxy-N-methylphenethylamine; D000584:Amiloride; D006632:Histamine; D012964:Sodium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid; D004005:Dichlorphenamide