Felipo V, Miñana M D, Grisolía S
Instituto de Investigaciones Citológicas de la Caja de Ahorros de Valencia, Centro Asociado del CSIC, Spain.
Arch Biochem Biophys. 1991 Mar;285(2):351-6. doi: 10.1016/0003-9861(91)90371-o.
Rats were fed a standard diet (20% protein) or a protein-free diet for up to 65 days. After 20 days on the protein-free diet some rats were refed the standard diet. By the 20th day the rats fed the protein-free diet showed a blood ammonia level approximately 70% higher than controls and urea excretion decreased approximately 20-fold. At this time the liver acetylglutamate decreased to approximately one-fifth of the initial and control levels, returning to normal after 3 days of refeeding the standard diet, with a concomitant increase in urea excretion. The protein-deficient diet resulted in decreased activities of liver enzymes related to ammonia metabolism. All enzyme activities assayed returned to normal values rapidly upon refeeding the standard diet, except hepatic carbamylphosphate synthetase, glutamine synthetase, and glutaminase, which took approximately 1 month to return to control values. The findings presented here are consistent with the view that urea production is controlled, at least under certain conditions, by acetylglutamate, the physiological activator of carbamylphosphate synthetase.
将大鼠喂以标准饮食（20%蛋白质）或无蛋白饮食长达65天。在无蛋白饮食20天后，一些大鼠重新喂以标准饮食。到第20天时，喂无蛋白饮食的大鼠血氨水平比对照组高约70%，尿素排泄量减少约20倍。此时，肝脏乙酰谷氨酸降至初始水平和对照水平的约五分之一，在重新喂以标准饮食3天后恢复正常，同时尿素排泄增加。蛋白质缺乏饮食导致肝脏中与氨代谢相关的酶活性降低。重新喂以标准饮食后，除肝氨甲酰磷酸合成酶、谷氨酰胺合成酶和谷氨酰胺酶外，所有检测的酶活性迅速恢复到正常值，这三种酶大约需要1个月才能恢复到对照值。此处呈现的研究结果与以下观点一致，即至少在某些条件下，尿素生成受氨甲酰磷酸合成酶的生理激活剂乙酰谷氨酸的控制。
