Premium
In Vivo Microdialysis of 2‐Deoxyglucose 6‐Phosphate into Brain
Author(s) -
Kintner D. B.,
Anderson M. E.,
Sailor K. A.,
Dienel G.,
Fitzpatrick James H.,
Gilboe D. D.
Publication year - 1999
Publication title -
journal of neurochemistry
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.75
H-Index - 229
eISSN - 1471-4159
pISSN - 0022-3042
DOI - 10.1046/j.1471-4159.1999.0720405.x
Subject(s) - chemistry , hypocapnia , bicarbonate , intracellular ph , phosphocreatine , microdialysis , in vivo , phosphate , inorganic phosphate , extracellular fluid , hypercapnia , analytical chemistry (journal) , chromatography , acidosis , extracellular , endocrinology , biochemistry , energy metabolism , biology , medicine , microbiology and biotechnology , organic chemistry
: A unique method for simultaneously measuring interstitial(pH e ) as well as intracellular (pH i ) pH in the brains oflightly anesthetized rats is described. A 4‐mm microdialysis probe wasinserted acutely into the right frontal lobe in the center of the area sampledby a surface coil tuned for the collection of 31 P‐NMR spectra.2‐Deoxyglucose 6‐phosphate (2‐DG‐6‐P) was microdialyzed into the rat until asingle NMR peak was detected in the phosphomonoester region of the 31 P spectrum. pH e and pH i values werecalculated from the chemical shift of 2‐DG‐6‐P and inorganic phosphate,respectively, relative to the phosphocreatine peak. The average in vivopH e was 7.24 ± 0.01, whereas the average pH i was7.05 ± 0.01 (n = 7). The average pH e value and the averageCSF bicarbonate value (23.5 ± 0.1 mEq/L) were used to calculate aninterstitial Pco 2 of 55 mm Hg. Rats were then subjected to a 15‐minperiod of either hypercapnia, by addition of CO 2 (2.5, 5, or 10%)to the ventilator gases, or hypocapnia (Pco 2 < 30 mm Hg), byincreasing the ventilation rate and volume. pH e responded inverselyto arterial Pco 2 and was well described ( r 2 =0.91) by the Henderson‐Hassel‐balch equation, assuming a pK a for the bicarbonate buffer system of 6.1 and asolubility coefficient for CO 2 of 0.031. This confirms the viewthat the bicarbonate buffer system is dominant in the interstitial space.pH i responded inversely and linearly to arterial Pco 2 .The intracellular effect was muted as compared with pH e (slope =‐0.0025, r 2 = 0.60). pH e and pH i values were also monitored during the first 12 min of ischemia produced bycardiac arrest. pH e decreases more rapidly than pH i during the first 5 min of ischemia. After 12 min of ischemia, pH e and pH i values were not significantly different (6.44 ± 0.02and 6.44 ± 0.03, respectively). The limitations, advantages, and futureuses of the combined microdialysis/ 31 P‐NMR method for measurementof pH e and pH i are discussed.