Abstract
A period of secondary energy failure consisting of a decline in phosphocreatine/inorganic phosphate (PCr/Pi), a rise in brain lactate, and alkaline intracellular pH (pHi) has been described in infants with neonatal encephalopathy. Strategies that ameliorate this energy failure may be neuroprotective. We hypothesized that a neonatal rat brain slice model undergoes a progressive decline in energetics, which can be ameliorated with hypothermia or amiloride. Interleaved phosphorus (31P) and proton (1H) magnetic resonance (MR) spectra were obtained from 350 μm neonatal rat brain slices over 8 h in a bicarbonate buffer at 37°C and at 32°C in 7- and 14-d models. 31P MR spectra were obtained with amiloride in a bicarbonate-free buffer at 37°C in the 14-d model. Findings were similar in 7- and 14-d models. In the 14-d model, there was a Pi doublet structure corresponding to alkaline pHi values of 7.50 ± 0.02 and 7.21 ± 0.04. Compared with the stabilized baseline of 100, at 5 h PCr/Pi was 65 ± 6.3 and lactate/NAA was 187 ± 3 at 37°C, but PCr/Pi and lactate/NAA were not significantly different from baseline at 32°C. Nucleotide triphosphate (NTP)/phosphomonoester (PME) was 0.93 ± 0.23 at 37°C and 1.81 ± 0.21 at 32°C at 5 h. With amiloride exposure in the 14-d model, baseline pHi values were 7.25 ± 0.09 and 6.98 ± 0.02 and NTP/PME was 1.81 ± 0.05; these parameters were not significantly different at 5 h. Our interpretation of these findings is that the brain slice model underwent secondary energy failure, which was delayed with hypothermia or amiloride.
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Abbreviations
- 1H:
-
proton
- KHB:
-
Krebs Henseleit buffer
- MR:
-
magnetic resonance
- MRS:
-
magnetic resonance spectroscopy
- Na+/H+ transporter:
-
sodium/proton transporter
- NE:
-
neonatal encephalopathy
- NTP:
-
nucleotide triphosphate
- 31P:
-
phosphorus
- PCr:
-
phosphocreatine
- pHi:
-
intracellular pH
- Pi:
-
inorganic phosphate
- PME:
-
phosphomonoester
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Supported by the Higher Education Funding Council for England, Imperial College London, Philips Medical Systems, and JEOL (UK) Ltd., which funded the 500 MHz magnetic resonance spectroscopy facility under the Joint Research Equipment Initiative.
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Robertson, N., Bhakoo, K., Puri, B. et al. Hypothermia and Amiloride Preserve Energetics in a Neonatal Brain Slice Model. Pediatr Res 58, 288–296 (2005). https://doi.org/10.1203/01.PDR.0000170899.90479.1E
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DOI: https://doi.org/10.1203/01.PDR.0000170899.90479.1E
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