脳灌流法による脳血流障害の研究 第2編 〔U-(14)C〕グルコースを用いた血流障害時の脳代謝

The brain was perfused with artificial blood containing [U-(14)C] glucose, and then induced the disturbances of cerebral blood flow as in the previous report. The changes in the glucose metabolism of the brain were studied by measuring oxigen consumption, carbon dioxide formation, glucose uptake and lactic acid output as well as the contents of glucose metabolites and their radioactivities. The results are presented as follows. 1. In the case where the cerebral blood flow is decreased 20% or less, the cerebral oxygen consumption maintains approximately a constant level; where the decrease is over 40% it decreases; and in the decrease of 20-30% both of the above phenomena can be observed. 2. As for carbon dioxide formation, likewise when the decrease is over 40%, the amount of carbon dioxide formed is decreased. 3. The glucose uptake is 0.44μmole in average before the cerebral blood flow is decreased, it is 0.12μmole 32-39 minutes after the cerebral blood flow is decreased, showing the decrease in proportion to the lapse of time. In addition, when the decrease of cerebral blood flow is over 40%, there is observed a decrease in the glucose uptake. With the lactic acid output there is observed no fixed tendency. 4. In the brain with blood flow disturbances the glycogen content is decreased to 1.65μmole. 5. The lactic acid content of the brain shows a tendency to increase when the cerebral blood flow is low. 6. The relative specific activity of metabolites in the brain under the diminished blocd flow, is found to be glucose 100%; lactic acid 45%; and in comparison to 63-75% of lactic acid in standard brain perfusion, the decrease in the radioactivity of lactic acid is marked in the brain with blood flow disturbances. This means that the contribution of non radioactive endogenous substances to the glycolytic process has been potentiated as compared with that in normal state. 7. The relative specific activity of glutamic acid, aspartic acid, glutamine and respiratory carbon dioxide are 30%, 32%, 17% and 20% respectively. In the standard perfusion these values are high in the high level of EEG, respective values being 80%, 75%, 61% and 55%, and it is known that the lower the EEG level, the lower is such ratios. However, these values in the brain with blood flow disturbances, agree approximately with those values in the brain with low function. 8. The relative specific actiyity of γ-amino butyric acid is 14% , being lower than that in the standard brain perfusion where the brain function is low. 9. The relative specific activity of glycogen, while it shows a big standard deviation, is about 22%, giving a considerably higher value than what has been expected. Even from the decrease of the glycogen content in the brain, it can be surmised that the involvement of glycogen in the energy metabolism in the brain under the blood flow disturbance is hightened. 10. These results seem to indicate that in the glucose metabolism of the brain with blood flow disturbances, there occur general disturbances of glucose uptake, glycolytic pathway and the citric acid cycle.