Effects of profound hypothermia on free amino acids in the cerebral cortex, especially on γ-aminobutyric acid, glutamic acid and aspartic acid, which have been believed to have intimate relationship to the cerebral function and metabolism, were studied in this report. Furthermore, effects of cytochrom C, pyridoxal phosphate and adenosine triphosphate on them in profound hypothermia were also investigated.
Until 25°C, γ-aminobutyric acid and glutamic acid were decreased, whereas aspartic acid was almost constant. At 20°C γ-aminobutyric acid and aspartic acid were increased, on the other hand glutamic acid was constant.
In the control group, in which respiration was not artificially maintained, γ-aminobutyric acid and glutamic acid were increased below 15°C and 10°C, respectively, while aspartic acid was almost constant.
In the group, in which respiration was artificially continued after respiratory arrest (respired group), patterns of alterations in the free amino acids were different between normothermia to 25°C, 25°C to 20°C, 20°C to 15°C and 15°C to 10°C. Among them, the alteration between 25 to 20°C and 20 to 15°C seemed to be most prominent.
Below 20°C, amounts of the 3 amino acids in the respired group were less than those in the control group.
Amounts of the 3 amino acids in the respired group during cooling were more than those in the rewarmed group, except that of γ-aminobutyric acid in the rewarmed group at 25-30°C, which means that recovery of amino acid content from hypothermia was started after that of γ-aminobutyric acid.
In the rewarmed group there was no difference in amino acid content between the group in which cardiac action and respiration were not resuscitated and the group in which only cardiac action was resuscitated, while there were prominent differences between the group in which only cardiac action was resuscitated and the group in which both cardiac action and respiration were resuscitated. Namely amounts of glutamic acid and aspartic acid in the former were more than those in the latter, but the difference of aspartic acid in both groups was statistically significant, but actually indefinite.
In the rewarmed group resuscitation of respiration prevented further increase of glutamic acid and accelerated decrease of aspartic acid. There was no relationship to resuscitation of the heart.
Cytochrom C delayed hypothermic change of γ-aminobutyric acid about 5°C and made hypothermic alterations of the other 2 amino acids less prominent.
Pyridoxal phosphate and adenosine triphosphate alleviated hypothermic alterations in the 3 amino acids.
On the results mentioned above, it was concluded that amounts of free γ-aminobutyric acid, glutamic acid and aspartic acid changed intimately with alterations of brain temperature, i.e. body temperature.
Cytochrom C, pyridoxal phosphate and adenosine triphosphate alleviated hypothermic changes in the 3 amino acids.