The Effect of Hyperthermia on Cerebral Energy Metabolism Studied with vivo 31P Nuclear Magnetic Resnance Spectrosccopy

Energy metabolism in the Wistar rat brain was studied by means of in vivo nuclear magnetic resonance spectroscopy after heating. The 31P-spectra were recorded at 10 minutes after heating the brain to 44 or 45℃ (cortical temperature) for 30 minutes on 6 rats in each group. Thereafter, the 31P-spectra were repeatedly recorded until 1 hour after heating. The 31P-spectra showed no significant changes of pH and high-energy phosphate levels occurred for 1 hour after heating of the brain to 44℃ for 30 minutes. However, those determined 10 minutes after heating the brain to 45℃ for 30 minutes showed a statistically significant reduction of the PCr/Pi ratio without accompaning a pH shift and change in ATP concentration. No further changes occurred thereafter for 1 hour after heating of the brain. The heat-induced PCr/Pi ratio reduction observed in this study reflected mitochondrial dysfunction and not a decline in cerebral blood flow. The present study has demonstrated at least part of the heat-induced damage of the brain occurred at mitochondrial level in vivo, while cerebral enerfy metabolism was found to be preserved up to cortical brain temperature of 44℃.

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