Semon B A, Leung P M, Rogers Q R, Gietzen D W
Department of Physiological Sciences, School of Veterinary Medicine, University of California, Davis 95616.
J Nutr. 1989 Feb;119(2):166-74. doi: 10.1093/jn/119.2.166.
Male Sprague-Dawley rats were trained to eat a 6% casein diet within a 3-h period each day. They were then fed a 6% casein diet for 10-16 d before they were fed either the same 6% casein diet or the 6% casein diet supplemented with 15% ammonium acetate for 1 or 7 d. During the absorptive period, plasma ammonia, plasma amino acids and brain amino acids were measured on d 1 and d 7 after feeding ammonium acetate. Food intake of rats fed 15% ammonium acetate was depressed on d 1 and increased to approximately 75% of the intake of the 6% casein-fed group by d 7. On d 1 plasma ammonia of the rats fed 5% ammonium acetate was 101 microM as compared to 56 microM for the rats fed 6% casein (P less than 0.05). On d 7, plasma ammonia of the rats fed 15% ammonium acetate was 240 microM (P less than 0.05) as compared to 44 microM for the rats fed 6% casein. In rats fed 15% ammonium acetate, after 7 d ornithine transcarbamylase and arginase activities were higher and argininosuccinate synthetase activity was lower (P less than 0.05) while carbamyl phosphate synthetase activity tended to be higher than that of rats fed 6% casein. The results suggest that rats adapt to ingestion of 15% ammonium acetate by some unknown neural mechanism rather than by increases in all urea cycle enzyme activities. Feeding ammonium acetate causes changes in plasma, brain and liver amino acid concentrations.
雄性斯普拉格-道利大鼠每天被训练在3小时内进食6%酪蛋白饮食。然后，在给它们喂食相同的6%酪蛋白饮食或添加15%醋酸铵的6%酪蛋白饮食1或7天之前，先让它们进食6%酪蛋白饮食10 - 16天。在吸收期，于喂食醋酸铵后的第1天和第7天测量血浆氨、血浆氨基酸和脑氨基酸。喂食15%醋酸铵的大鼠在第1天食物摄入量降低，到第7天时增加至6%酪蛋白喂养组摄入量的约75%。第1天，喂食5%醋酸铵的大鼠血浆氨为101微摩尔，而喂食6%酪蛋白的大鼠为56微摩尔（P < 0.05）。第7天，喂食15%醋酸铵的大鼠血浆氨为240微摩尔（P < 0.05），而喂食6%酪蛋白的大鼠为44微摩尔。在喂食15%醋酸铵的大鼠中，7天后鸟氨酸转氨甲酰酶和精氨酸酶活性较高，精氨琥珀酸合成酶活性较低（P < 0.05），而氨基甲酰磷酸合成酶活性倾向于高于喂食6%酪蛋白的大鼠。结果表明，大鼠通过某种未知的神经机制适应15%醋酸铵的摄入，而不是通过所有尿素循环酶活性的增加。喂食醋酸铵会导致血浆、脑和肝脏氨基酸浓度发生变化。
