Ammonia causes a drop in intracellular pH in metabolizing cortical brain slices. A [31P]- and [1H]nuclear magnetic resonance study.

Brooks, K. J. and Kauppinen, R. A. and Williams, S. R. and Bachelard, H. S. and Bates, T. E. and Gadian, D. G. (1989) Ammonia causes a drop in intracellular pH in metabolizing cortical brain slices. A [31P]- and [1H]nuclear magnetic resonance study. Neuroscience, 33 (1). pp. 185-192. ISSN 0306-4522

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Official URL: http://dx.doi.org/10.1016/0306-4522(89)90320-5

Abstract

[31P]- and [1H]Nuclear magnetic resonance spectroscopy were used to study metabolism in cortical brain slices in the guinea-pig during acute exposure to pathophysiological concentrations of ammonia. Intracellular acidification, measured from the chemical shift of endogenous inorganic phosphate, was observed without any change in cellular energy status or concentrations of lactate, glutamate and glutamine. The initial acidification, which developed over a period of 9 min appeared to be heterogeneous, on the basis of a splitting of the inorganic phosphate resonance in a number of experiments, corresponding to pH changes of 0.07 and 0.27 pH units. Subsequently a homogeneous acidification, of 0.15 pH units, developed by 23 min following exposure to ammonia. Intracellular pH recovered within 6 min after discontinuation of the ammonia load. In the absence of external bicarbonate, intracellular pH was 0.12 units more acidic than in the bicarbonate buffer and ammonia caused a further acidification by 0.16 units. When glutamine synthase inhibitor, methionine sulphoximine, was added, there was a slow fall in intracellular pH. Under these conditions, subsequent addition of ammonia failed to cause acidification directly. Thus acute elevation of ammonia does not lead to a change in cerebral high-energy phosphate or lactate metabolism, but may be associated with a fall in cortical intracellular pH.

Item Type:Article
Additional Information:[31P]- and [1H]Nuclear magnetic resonance spectroscopy were used to study metabolism in cortical brain slices in the guinea-pig during acute exposure to pathophysiological concentrations of ammonia. Intracellular acidification, measured from the chemical shift of endogenous inorganic phosphate, was observed without any change in cellular energy status or concentrations of lactate, glutamate and glutamine. The initial acidification, which developed over a period of 9 min appeared to be heterogeneous, on the basis of a splitting of the inorganic phosphate resonance in a number of experiments, corresponding to pH changes of 0.07 and 0.27 pH units. Subsequently a homogeneous acidification, of 0.15 pH units, developed by 23 min following exposure to ammonia. Intracellular pH recovered within 6 min after discontinuation of the ammonia load. In the absence of external bicarbonate, intracellular pH was 0.12 units more acidic than in the bicarbonate buffer and ammonia caused a further acidification by 0.16 units. When glutamine synthase inhibitor, methionine sulphoximine, was added, there was a slow fall in intracellular pH. Under these conditions, subsequent addition of ammonia failed to cause acidification directly. Thus acute elevation of ammonia does not lead to a change in cerebral high-energy phosphate or lactate metabolism, but may be associated with a fall in cortical intracellular pH.
Keywords:Ammonia, brain slices, NMR spectroscopy, 1H, 31P
Subjects:B Subjects allied to Medicine > B200 Pharmacology, Toxicology and Pharmacy
B Subjects allied to Medicine > B140 Neuroscience
Divisions:College of Science > School of Life Sciences
ID Code:5401
Deposited By: Timothy Bates
Deposited On:16 May 2012 06:03
Last Modified:16 May 2012 06:03

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