Free amino acids in the dog spinal cord during prolonged ischaemia

The authors studied the effect of 40 and 80 minutes' occlusion of the abdominal aorta on the aspartic acid, glutamic acid, glutamine, glycine and gamma-aminobutyric acid concentration in the sacral, lumbar, thoracic and cervical segments of the dog spinal cord. The most important changes were displayed by the glutamine concentration, which rose significantly after ischaemia in all the regions studied. The alanine and GABA concentration rose in the sacral and lumbar segments respectively, while the glutamic and aspartic acid concentrations in the sacral region fell. At the same time, enzyme activities degrading the synthetic substrates Leu-p-nitroanilide and Gly-p-nitroanilide increased. The significance of the findings is discussed with reference to nerve cell catabolism and function.