Effects in vivo and in vitro of l-glutamic acid-γ-hydrazide on metabolism of some free amino acids in brain and liver

Abstract

Further research on the effect of l-glutamic acid-γ-hydrazide (GAH) on free amino acids metabolism in brain is reported. Similar studies of free amino acid metabolism in liver are also presented. The addition of GAH to mice brain homogenates inhibited the activities of γ-aminobutyrate aminotransferase (ABAT), and of glutamate decarboxylase (GAD). The activities of alanine aminotransferase (AAA) and of aspartate aminotransferase (ASA) were not affected by GAH in these conditions. Brain homogenates from GAH-treated mice showed lower GAD, ABAT, AAA, and β-alanine-α-ketoglutaric aminotransferase (βAA) activities than brain homogenates from control mice. GAD activity was inhibited by GAH to a considerably lesser extent in vivo than in vitro. In liver, GAH produced a striking increase in the concentrations of almost all the free amino acids, especially of alanine and β-alanine. The addition of GAH to mice liver homogenates inhibited the βAA activity, but neither AAA nor ASA activity was affected by the same concentration of GAH. Liver homogenates from GAH-treated mice showed diminished βAA and AAA activity in comparison with liver homogenates from control mice. Some differences in the conversion of uniformly labeled 14C- glucose to liver and brain free amino acids were found between control and GAH-treated mice. In the brain of the latter animals, aspartic and glutamic acids and glutamine exhibited initially a higher specific activity than in control mice. In the case of γ-aminobutyric acid and alanine, opposite results were obtained. In the GAH-treated animals these two amino acids showed no significant decay of the acquired radioactivity. In liver, the decay of the acquired radioactivity of alanine tended to be slower in GAH-treated animals than in control animals.