| Autor: |
Kintner, D. B., Anderson, M. E., Sailor, K. A., Dienel, G., Fitzpatrick, James H., Gilboe, D. D. |
| Předmět: |
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| Zdroj: |
Journal of Neurochemistry; Jan99, Vol. 72 Issue 1, p405, 8p, 1 Diagram, 1 Chart, 9 Graphs |
| Abstrakt: |
Abstract: A unique method for simultaneously measuring interstitial(pH[sub e]) as well as intracellular (pH[sub 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 [sup 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[sup 31]P spectrum. pH[sub e] and pH[sub 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[sub e] was 7.24 ± 0.01, whereas the average pH[sub i] was7.05 ± 0.01 (n = 7). The average pH[sub e] value and the averageCSF bicarbonate value (23.5 ± 0.1 mEq/L) were used to calculate aninterstitial Pco[sub 2] of 55 mm Hg. Rats were then subjected to a 15-minperiod of either hypercapnia, by addition of CO[sub 2] (2.5, 5, or 10%)to the ventilator gases, or hypocapnia (Pco[sub 2] < 30 mm Hg), byincreasing the ventilation rate and volume. pH[sub e] responded inverselyto arterial Pco[sub 2] and was well described (r[sup 2] =0.91) by the Henderson-Hassel-balch equation, assuming apK[sub a] for the bicarbonate buffer system of 6.1 and asolubility coefficient for CO[sub 2] of 0.031. This confirms the viewthat the bicarbonate buffer system is dominant in the interstitial space.pH[sub i] responded inversely and linearly to arterial Pco[sub 2].The intracellular effect was muted as compared with pH[sub e] (slope =-0.0025, r[sup 2] = 0.60). pH[sub e] and pH[sub i]values were also monitored during the first 12 min of ischemia produced bycardiac arrest. pH[sub e] decreases more rapidly than pH[sub i]during the first 5 min of ischemia. After 12 min of ischemia, pH[sub e]and pH[sub i] values were not significantly different (6.44 ± 0.02and 6.44 ± 0.03, respectively).... [ABSTRACT FROM AUTHOR] |
| Databáze: |
Complementary Index |
| Externí odkaz: |
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