title: Regulation of intracellular pH in cultured bovine retinal pigment epithelial cells.
abstract: Regulation of intracellular pH (pHi) in bovine retinal pigment epithelium (RPE) was investigated in cell culture. pHi was measured using the pH-sensitive absorbance of intracellularly trapped 5 (and 6)-carboxy-dimethyl-fluorescein (CDMF). (1) Regulation of pHi after induction of an acid load by removal of NH4Cl could be blocked either totally by removal of extracellular sodium, or subtotally (about 90%) by application of amiloride (1 mmol/l). Additional flux measurements revealed a dose-dependent, amiloride-sensitive 22Na+-uptake into Na+-loaded cells. Both results suggest the presence of a Na+/H+ antiport. (2) When alkalinization of the cells was induced by preincubation with 50 mmol/l acetate in HCO3(-)-Ringer's and subsequent removal of the weak acid, the following regulation was dependent on the presence of extracellular chloride. This process could be blocked with DIDS (1 mmol/l), suggesting the presence of a Cl-/HCO3- exchange mechanism. (3) We found no evidence for a Na+/HCO3(-)-cotransport, which had been postulated to be present in RPE by others. We conclude that two processes are involved in regulation of pHi in RPE: A Na+/H+ antiport responsible for recovery of pHi from acid load, and a DIDS-sensitive Cl-/HCO3- exchange mechanism responsible for recovery of pHi after alkalinization.
authors.affiliation: Institut für Klinische Physiologie, Freie Universität Berlin.
authors.forename: S K
authors.initials: SK
authors.lastname: Keller
authors.forename: T J
authors.initials: TJ
authors.lastname: Jentsch
authors.forename: I
authors.initials: I
authors.lastname: Janicke
authors.forename: M
authors.initials: M
authors.lastname: Wiederholt
mesh_terms: D000818:Animals; D001692:Biological Transport; D001826:Body Fluids / Q000502:physiology*; D002417:Cattle; D002478:Cells, Cultured; D006863:Hydrogen-Ion Concentration; D007424:Intracellular Fluid / Q000502:physiology*; D007474:Ion Exchange; D010857:Pigment Epithelium of Eye / Q000166:cytology / Q000502:physiology*; D011522:Protons; D012964:Sodium / Q000493:pharmacokinetics
chemical_list: D011522:Protons; D012964:Sodium