Wilke A, Simon O, Bergner H
Arch Tierernahr. 1984 Nov;34(11):749-60. doi: 10.1080/17450398409425726.
40 rats with a body weight of 100 g received 7 semisynthetic diets with different contents of glutamic acid and one diet contained whole egg. A L-amino acid mixture corresponding to the pattern of egg protein was the protein source of the semisynthetic diets. Glutamic acid was supplemented successively from 0 to 58 mol-% of the total amino acid content. On the 8th day of experimental feeding the animals were labelled by subcutaneous injection of 14C-U-L-glutamic acid. Subsequently the CO2- and the 14CO2-excretion were measured for 24 hours. In this period 64 to 68% of the injected radioactivity were recovered as 14CO2. The curve pattern of 14CO2-excretion indicates two different processes of 14CO2-formation. One characterizing the direct degradation of glutamic acid to CO2 with a high rate constant and a second one with a lower rate constant characterizing the 14CO2-formation via metabolites of glutamic acid. 77% of the total 14CO2-excretion in 24 hours resulted from the direct oxidation of glutamic acid and 23% from the oxidation of intermediates. When 14CO2-formation was measured 10 to 24 hours after injection of 14C-glutamic acid a positive correlation to the content of glutamic acid in the diet was observed. The intestinal tissue contribute considerably to the catabolization of glutamic acid, however, there seems to exist an upper limit for this capacity.
40只体重为100克的大鼠接受了7种谷氨酸含量不同的半合成日粮，另一种日粮含有全蛋。一种与鸡蛋蛋白质模式相对应的L-氨基酸混合物是半合成日粮的蛋白质来源。谷氨酸的添加量依次从总氨基酸含量的0增加到58摩尔%。在实验喂养的第8天，通过皮下注射14C-U-L-谷氨酸对动物进行标记。随后测量24小时内的二氧化碳和14二氧化碳排泄量。在此期间，64%至68%的注射放射性以14二氧化碳的形式回收。14二氧化碳排泄的曲线模式表明了14二氧化碳形成的两个不同过程。一个过程以高速率常数表征谷氨酸直接降解为二氧化碳，另一个过程以较低速率常数表征通过谷氨酸代谢产物形成14二氧化碳。24小时内总14二氧化碳排泄量的77%来自谷氨酸的直接氧化，23%来自中间体的氧化。当在注射14C-谷氨酸后10至24小时测量14二氧化碳的形成时，观察到与日粮中谷氨酸含量呈正相关。肠道组织对谷氨酸的分解代谢有很大贡献，然而，这种能力似乎存在一个上限。
