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Intracellular pH regulation in primary rat astrocytes and C6 glioma cells.

Abstract
We used the pH-sensitive fluorescent dye BCECF to study intracellular pH (pHi) regulation in primary cultures of rat astrocytes and C6 glioma cells. Both cell types contain three pH-regulating transporters: 1) alkalinizing Na+/H+ exchange; 2) alkalinizing Na+ + HCO3-/Cl- exchange; and 3) acidifying Cl-/HCO3- exchange. Na+/H+ exchange was most evident in the absence of CO2; recovery from acidification was Na+ dependent and amiloride sensitive. Exposure to CO2 caused a cell alkalinization that was inhibited by DIDS, dependent on external Na+, and inhibited 75% in the absence of Cl- (thus mediated by Na+ + HCO3-/Cl- exchange). When pHi was increased above the normal steady-state pHi, a DIDS-inhibitable and Na(+)-independent acidifying recovery was evident, indicating the presence of Cl-/HCO3- exchange. Astrocytes, but not C6 cells, contain a fourth pH-regulating transporter, Na(+)-HCO3- cotransport; in the presence of CO2, depolarization caused an alkalinization of 0.12 +/- 0.01 (n = 8) and increased the rate of CO2-induced alkalinization from 0.23 +/- 0.02 to 0.42 +/- 0.03 pH unit/min. Since C6 cells lack the Na(+)-HCO3- cotransporter, they are an inferior model of pHi regulation in glia. Our results differ from previous observations in glia in that: 1) Na+/H+ exchange was entirely inhibited by amiloride; 2) Na+ + HCO3-/Cl- exchange was present and largely responsible for CO2-induced alkalinization; 3) Cl-/HCO3- exchange was only active at pHi values above steady state; and 4) depolarization-induced alkalinization of astrocytes was seen only in the presence of CO2.
AuthorsL D Shrode, R W Putnam
JournalGlia (Glia) Vol. 12 Issue 3 Pg. 196-210 (Nov 1994) ISSN: 0894-1491 [Print] United States
PMID7851988 (Publication Type: Comparative Study, Journal Article, Research Support, Non-U.S. Gov't, Research Support, U.S. Gov't, Non-P.H.S.)
Chemical References
  • Antiporters
  • Carrier Proteins
  • Chloride-Bicarbonate Antiporters
  • Sodium-Bicarbonate Symporters
  • Sodium-Hydrogen Exchangers
  • Carbon Dioxide
  • Potassium
Topics
  • Animals
  • Antiporters (metabolism)
  • Astrocytes (metabolism, physiology)
  • Carbon Dioxide (pharmacology)
  • Carrier Proteins (metabolism)
  • Chloride-Bicarbonate Antiporters
  • Electrophysiology
  • Glioma (metabolism, pathology, physiopathology)
  • Homeostasis
  • Hydrogen-Ion Concentration
  • Intracellular Membranes (metabolism)
  • Potassium (pharmacology)
  • Rats
  • Rats, Sprague-Dawley
  • Sodium-Bicarbonate Symporters
  • Sodium-Hydrogen Exchangers (metabolism)
  • Tumor Cells, Cultured

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