Lowenstein J M, Goodman M N
Fed Proc. 1978 Jul;37(9):2308-12.
The following evidence demonstrates that ammonia production in muscle occurs via the reactions of the purine nucleotide cycle: i) Extracts of cytosol which lack glutamine dehydrogenase produce ammonia under conditions that mimic muscle doing work. In such extracts a member of the purine nucleotide cycle (AMP, IMP, or adenylosuccinate) must be present in order that ammonia production can take place, ii) Perfused hindleg of rat or hindleg in situ produces ammonia during exercise, and there is a concomitant production of IMP and adenylosuccinate. Exercise causes a decrease in the contents of glutamate, aspartate, and glutamine and an increase in the content of alanine of perfused hindleg of rat. However, output of alanine does not change or is diminished during exercise. Glutamine output is diminished by exercise. Epinephrine increases the output and tissue content of ammonia and glutamine. It decreases the output and content of alanine, and it decreases the contents of aspartate and glutamate.
以下证据表明，肌肉中的氨生成是通过嘌呤核苷酸循环的反应进行的：i）缺乏谷氨酰胺脱氢酶的胞质溶胶提取物在模拟肌肉做功的条件下会产生氨。在这种提取物中，必须存在嘌呤核苷酸循环的一个成员（AMP、IMP或腺苷酸琥珀酸）才能产生氨；ii）大鼠的灌注后肢或原位后肢在运动过程中会产生氨，同时会产生IMP和腺苷酸琥珀酸。运动导致大鼠灌注后肢中谷氨酸、天冬氨酸和谷氨酰胺的含量降低，丙氨酸的含量增加。然而，运动期间丙氨酸的输出量不变或减少。运动使谷氨酰胺的输出量减少。肾上腺素会增加氨和谷氨酰胺的输出量及组织含量。它会降低丙氨酸的输出量和含量，还会降低天冬氨酸和谷氨酸的含量。
