Abstract
In an attempt to study on metabolic changes in rats fed an amino acid diet devoid of an essential amino acid, rats were force-fed a phenylalanine-free, phenylalanine and tyrosine-free or complete amino acid diet for 4 days and killed 3 hours after the feeding on day 5. The urinary nitrogen and N'methylnicotinamide (MNA), the tryptophan pyrrolase (TPase) and tyrosine-α-ketoglutarate transaminase (TKase) activities of liver, and the fat content of liver were estimated. Beside, in order to clarify the effect of amino acid patterns of diets on the liver TPase and TKase activities, intact and adrenalectomized rats were administered a threonine-free or complete amino acid diet and sacrificed three hours later.
The results indicated that the urinary nitrogen and MNA, the TPase and TKase activities of liver, and the fat content in liver of rats fed the phenylalanine-free or phenylalanine and tyrosine-free diet were higher than those of rats fed the complete amino acid diet. Both of liver enzyme activities of adrenalectomized rats force-fed the threonine-free or complete amino acid diet were lower than those of intact rats fed the same diet respectively. Furthermore, the TPase activity of adrenalectomized rats fed the threonine-free diet was higher than that fed the complete amino acid diet, whereas, the liver TKase activities in both diet groups of adrenalectomized rats were almost the same level.
These results demonstrated that the TPase activity could be directly affected by the utilization of tryptophan in diets in this experimental condition, whereas changes in TKase activity depended on the function of adrenal gland in preference to the direct effect of amino acid patterns in diets.
