Metabolism of hibernating reptiles. Changes of free amino acids in blood, liver and brain.

1. Glutamic acid showed a significant decrease during hibernation in brain cortex. This is attributed to: (a) Transformation to glutamine to detoxicate ammonia. (b) The synthesis of GABA from glutamic acid. (c) It is suggested that the enzyme GAD is active during hibernation. 2. GABA showed a significant increase in liver and brain cortex. It was absent in the blood serum. (a) The present results show that non-neural tissues contain lower GABA than neural tissues. (b) GABA may be formed locally in tissues by decarboxylation of glutamate as well as from pathways connected with tricarboxylic acid cycle. 3. Aspartic acid showed increased levels in blood serum, liver and brain cortex, the greatest increase was observed in liver. 4. A significant increase was recorded in the level of arginine in brain cortex and liver, whilst a smaller percentage increase was recorded in ornithine level. It is assumed that transformation of arginine to ornithine was depressed during hibernation.