Electrogenic Na+/HCO3- cotransport in neuroglia.
Membrane potential recording from glial cells in Necturus optic nerve in the presence of 2 mM Ba++, which was added to block the K+ conductance, gave the following results. 1) In HCO3- -free, low-Na+ solutions (11% of control; Na+ replaced with N-methyl-D-glucamine), the hyperpolarizing effect of adding 10 mM HCO3- was reduced by approximately 80%. 2) 4-acetamido-4'-isothiocyanato-stilbene-2,2'-disulfonic acid (SITS, 0.1 or 1 mM) reduced the effect of HCO3- by at least 50%. 3) In the presence of HCO3-, reduction of Na+ caused a depolarization which was much larger than that observed in nominally HCO3- -free solutions. These observations indicate the presence in the glial membrane of an electrogenic Na+/HCO3- cotransporter in which the stoichiometry of HCO3- to Na+ is greater than 1.
Astion
M L
ML
Institute of Neurobiology, University of Puerto Rico Medical Sciences Campus, Old San Juan.
Orkand
R K
RK
D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D001693:Biological Transport, Active; D002352:Carrier Proteins / Q000378:metabolism; D004563:Electrochemistry; D066298:In Vitro Techniques; D008564:Membrane Potentials; D009337:Necturus; D009457:Neuroglia / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D027982:Sodium-Bicarbonate Symporters
D001639:Bicarbonates; D002352:Carrier Proteins; D027982:Sodium-Bicarbonate Symporters; D012964:Sodium