Yamamoto Y, Katayama H, Muramatsu K
J Nutr Sci Vitaminol (Tokyo). 1976;22(6):467-75. doi: 10.3177/jnsv.22.467.
The growth retardation and external pathological lesions that occur in rats fed a 10% casein diet containing 5% tyrosine could be alleviated by the supplementation of extra protein (20% casein) or 0.66% methionine plus 0.90% threonine (equivalent to the contents in a 20% casein, respectively). Liver tyrosine aminotransferase activity is elevated by ingestion of excess tyrosine, but lowered by the supplementation of extra casein of methionine plus threonine. In rats fed a high tyrosine diet supplemented with methionine plus threonine, liver p-hydroxyphenylpyruvate hydroxylase activity was not higher than that of the 10% casein group, but liver homogentisate oxidase activity increased significantly. When excess tyrosine was included in the 10% casein diet, free tyrosine concentrations in plasma, liver, muscle and brain were extremely elevated, but when the high tyrosine diet was supplemented with extra casein or methionine plus threonine, their plasma and tissues tyrosine concentrations lowered significantly. A large increase in total phenols, p-hydroxyphenylpyruvate and free tyrosine excretions in urine was produced in animals fed the high tyrosine-low protein diet, but these were lowered by the supplementation of methionine and threonine to the diet.
给大鼠喂食含5%酪氨酸的10%酪蛋白饮食时出现的生长迟缓及外部病理损伤，可通过补充额外蛋白质（20%酪蛋白）或0.66%蛋氨酸加0.90%苏氨酸（分别相当于20%酪蛋白中的含量）得到缓解。摄入过量酪氨酸会使肝脏酪氨酸转氨酶活性升高，但补充额外的酪蛋白、蛋氨酸加苏氨酸则会使其降低。在喂食补充了蛋氨酸加苏氨酸的高酪氨酸饮食的大鼠中，肝脏对羟基苯丙酮酸羟化酶活性并不高于10%酪蛋白组，但肝脏尿黑酸氧化酶活性显著增加。当10%酪蛋白饮食中含有过量酪氨酸时，血浆、肝脏、肌肉和大脑中的游离酪氨酸浓度会极度升高，但在高酪氨酸饮食中补充额外的酪蛋白或蛋氨酸加苏氨酸后，其血浆和组织中的酪氨酸浓度会显著降低。喂食高酪氨酸-低蛋白饮食的动物尿液中总酚、对羟基苯丙酮酸和游离酪氨酸的排泄量大幅增加，但在饮食中补充蛋氨酸和苏氨酸后，这些排泄量会降低。
