Addition of carbonic anhydrase augments extracellular pH buffering in rat cerebral cortex.
1. The ability of the extracellular space to buffer rapid alkaline shifts was studied in rat cortex in vitro and in vivo. Alkaline shifts were generated by iontophoresis of OH- or were evoked by pressure ejection of alpha-amino-3-hydroxy-5-methylisoxazole-4-propionic acid (AMPA). 2. In cortical slices, alkaline shifts induced by OH- were enhanced by the carbonic anhydrase (CA) inhibitor benzolamide (83 +/- 16%, mean +/- SE), and were decreased by superfusion of 10 mg/l CA (-59 +/- 4%). CA had no effect at 1 mg/l, and no additional effect at 100 mg/l. 3. In slices, and in vivo, alkaline shifts induced by AMPA were similarly enhanced by benzolamide and decreased by superfusion of CA. 4. These data indicate that extracellular CA activity is less than that required for maximum buffering. This suggests that equilibrium between CO2 and bicarbonate may not be attained during rapid extracellular pH shifts.
Huang
W
W
Department of Physiology, New York University Medical Center, New York 10016, USA.
Smith
S E
SE
Chesler
M
M
D000375:Aging / Q000378:metabolism; D000468:Alkalies / Q000378:metabolism; D000818:Animals; D000831:Animals, Newborn / Q000254:growth & development / Q000378:metabolism; D002021:Buffers; D002256:Carbonic Anhydrases / Q000494:pharmacology*; D002540:Cerebral Cortex / Q000378:metabolism*; D018690:Excitatory Amino Acid Agonists / Q000494:pharmacology; D005110:Extracellular Space / Q000378:metabolism*; D005260:Female; D006859:Hydrogen / Q000378:metabolism*; D006863:Hydrogen-Ion Concentration; D017665:Hydroxyl Radical / Q000494:pharmacology; D008297:Male; D051381:Rats; D011919:Rats, Inbred Strains; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid / Q000494:pharmacology
D000468:Alkalies; D002021:Buffers; D018690:Excitatory Amino Acid Agonists; D017665:Hydroxyl Radical; D018350:alpha-Amino-3-hydroxy-5-methyl-4-isoxazolepropionic Acid; D006859:Hydrogen; D002256:Carbonic Anhydrases