Abbreviations used : 2-DG-6-P, 2-deoxyglucose 6-phosphate ; FID, free induction decay ; PCr, phosphocreatine ; pHe, interstitial pH ; pHi, intracellular pH ; PME, phosphomonoester.
In Vivo Microdialysis of 2-Deoxyglucose 6-Phosphate into Brain
A Novel Method for the Measurement of Interstitial pH Using 31P-NMR
Article first published online: 18 JAN 2002
Journal of Neurochemistry
Volume 72, Issue 1, pages 405–412, January 1999
How to Cite
Kintner, D. B., Anderson, M. E., Sailor, K. A., Dienel, G., Fitzpatrick, J. H. and Gilboe, D. D. (1999), In Vivo Microdialysis of 2-Deoxyglucose 6-Phosphate into Brain. Journal of Neurochemistry, 72: 405–412. doi: 10.1046/j.1471-4159.1999.0720405.x
- Issue published online: 18 JAN 2002
- Article first published online: 18 JAN 2002
- 2-Deoxyglucose 6-phosphate;
- Intracellular pH;
- Interstitial pH;
Abstract : A unique method for simultaneously measuring interstitial (pHe) as well as intracellular (pHi) pH in the brains of lightly anesthetized rats is described. A 4-mm microdialysis probe was inserted acutely into the right frontal lobe in the center of the area sampled by a surface coil tuned for the collection of 31P-NMR spectra. 2-Deoxyglucose 6-phosphate (2-DG-6-P) was microdialyzed into the rat until a single NMR peak was detected in the phosphomonoester region of the 31P spectrum. pHe and pHi values were calculated from the chemical shift of 2-DG-6-P and inorganic phosphate, respectively, relative to the phosphocreatine peak. The average in vivo pHe was 7.24 ± 0.01, whereas the average pHi was 7.05 ± 0.01 (n = 7). The average pHe value and the average CSF bicarbonate value (23.5 ± 0.1 mEq/L) were used to calculate an interstitial Pco2 of 55 mm Hg. Rats were then subjected to a 15-min period of either hypercapnia, by addition of CO2 (2.5, 5, or 10%) to the ventilator gases, or hypocapnia (Pco2 < 30 mm Hg), by increasing the ventilation rate and volume. pHe responded inversely to arterial Pco2 and was well described (r2 = 0.91) by the Henderson-Hassel-balch equation, assuming a pKa for the bicarbonate buffer system of 6.1 and a solubility coefficient for CO2 of 0.031. This confirms the view that the bicarbonate buffer system is dominant in the interstitial space. pHi responded inversely and linearly to arterial Pco2. The intracellular effect was muted as compared with pHe (slope = -0.0025, r2 = 0.60). pHe and pHi values were also monitored during the first 12 min of ischemia produced by cardiac arrest. pHe decreases more rapidly than pHi during the first 5 min of ischemia. After 12 min of ischemia, pHe and pHi values were not significantly different (6.44 ± 0.02 and 6.44 ± 0.03, respectively). The limitations, advantages, and future uses of the combined microdialysis/31P-NMR method for measurement of pHe and pHi are discussed.