title: Cytoplasmic pH regulation in macrophages by an ATP-dependent and N,N'-dicyclohexylcarbodiimide-sensitive mechanism. Possible involvement of a plasma membrane proton pump.
abstract: Cytoplasmic pH (pHi) regulation was studied in thioglycolate-elicited murine macrophages using fluorescent probes. Acid-loaded macrophages regained normal pHi by extrusion of H+ equivalents across the plasma membrane. A fraction of this recovery was due to Na+/H+ exchange, as evidenced by its partial Na+ dependence and amiloride sensitivity. The residual, Na+-independent pHi recovery (approximately 50% of the total) persisted in the nominal absence of HCO3- and was insensitive to disulfonic stilbenes, ruling out mediation by anion exchange. In contrast, intracellular alkalinization and H+ extrusion from the cells were inhibited by N-ethylmaleimide, by N,N'-dicyclohexylcarbodiimide or by prior depletion of intracellular ATP. These observations are consistent with the existence of a H+-pumping ATPase in the plasma membrane of macrophages. The mechanism of activation of the ATP-dependent H+ extrusion process was also investigated. In other systems, Ca2+ mobilization has been suggested to signal an exocytic insertion of H+ pumps into the plasma membrane. Acid loading of macrophages was accompanied by an elevation of the cytosolic Ca2+ concentration ([Ca2+]i), measured using indo-1. These results are consistent with a role for Ca2+ mobilization in the activation of H+ extrusion.
authors.affiliation: Department of Surgery, Toronto General Hospital, Ontario, Canada.
authors.forename: C J
authors.initials: CJ
authors.lastname: Swallow
authors.forename: S
authors.initials: S
authors.lastname: Grinstein
authors.forename: O D
authors.initials: OD
authors.lastname: Rotstein
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism*; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D002234:Carbodiimides / Q000494:pharmacology*; D002352:Carrier Proteins / Q000378:metabolism; D002462:Cell Membrane / Q000378:metabolism; D003078:Colchicine / Q000494:pharmacology; D003593:Cytoplasm / Q000378:metabolism; D004024:Dicyclohexylcarbodiimide / Q000494:pharmacology*; D005260:Female; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D008264:Macrophages / Q000187:drug effects / Q000378:metabolism*; D051379:Mice; D009550:Nigericin / Q000494:pharmacology; D006180:Proton-Translocating ATPases / Q000378:metabolism; D017923:Sodium-Hydrogen Exchangers
chemical_list: D002234:Carbodiimides; D002352:Carrier Proteins; D017923:Sodium-Hydrogen Exchangers; D004024:Dicyclohexylcarbodiimide; D000584:Amiloride; D000255:Adenosine Triphosphate; D006180:Proton-Translocating ATPases; D009550:Nigericin; D003078:Colchicine