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KMID : 0378019600030110069
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New Medical Journal
1960 Volume.3 No. 11 p.69 ~ p.80
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Studies on the Effects of Phrenotropic Agents on the Metabolism of Amino Acids
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Abstract
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The present report deals with the influence of phrenotropic agents on the transamination in the metabolism of tryptophan. The changes of the activities of
tryptophan pyrrolase, glutamic pyruvic transaminase and glutamic-oxaloacetic transaminase of liver and brain were determined in vitro and in vivo (rat) following the treatment with chlorpromazine, JB-516 and iproniazid. The effects of bydroxylamine were also examined on these preparations.
Results:
1. Chlorpromazine increased the activities of tryptophan pyrrolase (about 70%) and glutamic-pyruvic transaminase (about 30%) but decreased the activity of glutamic oxaloacetic transaminase of liver. The activity of glutamic-oxaloacetic transaminase of brain i was not changed after the treatment with chlorpromazine. The mechanism of increasing activities of tryptophan pyrrolase and glutamic-pyruvic transaminase of liver may be due to an increased secretion of adrenal cortical hormones through the stimulation of ACTH secretion following the administration of chlorpromazine in vivo. On the contrary, chlorpromazine exhibited no effects on the activities of the above enzyme systems in vitro.
2. JB-516 and iproniazid inhibited the activity of tryptophan pyrrolase (about 25%). Iproniazid remarkably inhibited the activity of glutamic-pyruvic transaminase in the materials prepared both from liver and brain but JB-516 inhibited only that prepared i from. brain. The inhibition of the activity of glutamic-
oxaloacetic transaminase of liver and brain (each 50%) by these agents markedly decreased than that of glutamic-pyruvic transaminase.
In vitro experiments JB-516 has been shown to inhibit markedly the activities of glutamic-oxaloacetic transaminase and glutamic-pyruvic transaminase of liver but slightly inhibited- that of tryptophan pyrrolase only in high concentrations: Iproniazid did not affect the activities of these enzymes in vitro.
3. Hydroxylamine inhibited the activity of tryptophan pyrrolase in vivo as well as in vitro. It also inhibited the activities of glutamic-oxaloacetic transaminase of liver and brain and glutamic-pyruvic transaminase of fiver in proportion with the concentrations of this compound. The inhibition of latter was more marked than that of the former.
In considering the fact that these agents except chlorpromazine are the inhibitors of catalase and hemoglobin, the inhibition of tryptophan pyrrolase by these agents is plausible because this enzyme contains porphyrin prosthetic group. However, the exact mechanism of this inhibition is not clear whether these agents interfere with the de novo synthesis of the enzyme protein or render the enzyme in the state of inactivation.
The influence of these agents on the oxidative 4eamination of 5-hydroxytryptamine and norepinephrir.e is also discussed in connection with the results obtained from our experiments.
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