Intracellular pH shifts capable of uncoupling cultured oligodendrocytes are seen only in low HCO3- solution.
Electrical coupling between cultured mouse oligodendrocytes was transiently blocked when pHi was decreased below about 6.5 using the NH4+ prepulse method. This uncoupling could, however, only be achieved if the dominant pHi regulating mechanism in these cells, the Na+/HCO3- cotransporter, was blocked by lowering bath [HCO3-]. Under this condition, an NH4+ prepulse caused pHi to decrease toward the passive distribution for H+ (i.e., about pH 6.2). In the presence of normal bath [HCO3-] an NH4+ prepulse did not decrease pHi below 6.5 even when the second pHi regulating mechanism, the Na+/H+ exchanger, was blocked by amiloride, and consequently oligodendrocytes could not be uncoupled. Increasing CO2, which uncouples glial cells in situ (Connors et al: J. Neurosci. 4:1324-1330, 1984), did not uncouple cultured oligodendrocytes in the presence of normal bath [HCO3-], but did cause uncoupling in low [HCO3-] solution. These results indicate that electrical coupling between cultured oligodendrocytes is sensitive to pHi; in normal bath [HCO3-], however, the pHi regulation of these cells is so effective that standard techniques for intracellular acidification are unable to lower pHi to levels which cause the closure of oligodendrocyte gap junctions.
Kettenmann
H
H
Department of Neurobiology, University of Heidelberg, Federal Republic of Germany.
Ransom
B R
BR
Schlue
W R
WR
D000818:Animals; D001639:Bicarbonates / Q000494:pharmacology*; D002478:Cells, Cultured; D005665:Furosemide / Q000494:pharmacology; D006863:Hydrogen-Ion Concentration; D007365:Intercellular Junctions / Q000187:drug effects / Q000502:physiology*; D008564:Membrane Potentials / Q000187:drug effects; D051379:Mice; D009836:Oligodendroglia / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D051381:Rats
D001639:Bicarbonates; D005665:Furosemide