Regulation of intracellular pH in pyramidal neurones from the rat hippocampus by Na(+)-dependent Cl(-)-HCO3- exchange.
1. We have measured intracellular pH (pHi) in freshly isolated pyramidal neurones from the CA1 region of the rat hippocampus using the fluorescent indicator 2',7'-bis(carboxy-ethyl)-5-(and-6)-carboxyfluorescein (BCECF). 2. The neurones selected by our isolation procedure, when studied in the nominal absence of CO2-HCO3-, had a mean steady-state pHi of 6.81 +/- 0.02 (n = 163). The recovery of pHi from acid loads was very slow. The rate of recovery from acid loads was reduced by Na+ removal, but only very slightly inhibited by 1 mM amiloride. 3. The addition of 5% CO2-25 mM HCO3- caused steady-state pHi to increase from 6.74 +/- 0.05 to 7.03 +/- 0.03 (n = 28). In the presence of 5% CO2-25 mM HCO3-, the rate of pHi recovery from acid loads was much faster than in its absence. 4. The HCO(3-)-induced alkalinization was reversible, and did not occur in the absence of extracellular Na+ or in the presence of DIDS (4,4'-diisothiocyanatostilbene- 2,2'-disulphonic acid). 5. In the absence of external Cl-, successive exposures to CO2-HCO3- elicited alkalinizations that were progressively reduced in rate and amplitude. This effect, presumably due to gradual depletion of internal Cl-, was rapidly reversed by returning Cl- to the external medium. 6. We conclude that the major acid-extrusion mechanism in pyramidal CA1 neurones is the Na(+)-dependent Cl(-)-HCO3- exchanger. The Na(+)-dependent mechanism that operates in the nominal absence of HCO3- is far less active.
Schwiening
C J
CJ
Department of Cellular and Molecular Physiology, Yale University School of Medicine, New Haven, CT 06510.
Boron
W F
WF
D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid / Q000494:pharmacology; D000584:Amiloride / Q000494:pharmacology; D000818:Animals; D001639:Bicarbonates / Q000378:metabolism*; D002245:Carbon Dioxide / Q000494:pharmacology; D002712:Chlorides / Q000378:metabolism*; D005452:Fluoresceins; D005456:Fluorescent Dyes; D006624:Hippocampus / Q000166:cytology / Q000187:drug effects / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D066298:In Vitro Techniques; D007474:Ion Exchange; D017966:Pyramidal Cells / Q000187:drug effects / Q000378:metabolism*; D051381:Rats; D017207:Rats, Sprague-Dawley; D012964:Sodium / Q000502:physiology*; D013050:Spectrometry, Fluorescence
D001639:Bicarbonates; D002712:Chlorides; D005452:Fluoresceins; D005456:Fluorescent Dyes; D002245:Carbon Dioxide; D000584:Amiloride; C043829:2',7'-bis(carboxyethyl)-5(6)-carboxyfluorescein; D012964:Sodium; D017878:4,4'-Diisothiocyanostilbene-2,2'-Disulfonic Acid