Inoue I, Gushiken T, Kobayashi K, Saheki T
Department of Biochemistry, Faculty of Medicine, Kagoshima University, Japan.
Biochem Med Metab Biol. 1987 Dec;38(3):378-86. doi: 10.1016/0885-4505(87)90102-2.
Sparse-fur mice which are deficient in ornithine transcarbamylase, the second-step enzyme in the urea cycle, were examined for hyperammonemia and its relationship with encephalopathy. We compared amino acid concentrations in the serum and brain of spf mice with those of control mice. Unlike hepatic encephalopathy we could not find marked amino acid changes in the serum of spf mice besides low levels of citrulline and arginine. But in the brain of spf mice, glutamine was increased strikingly during hyperammonemia, and a concomitant accumulation of large neutral amino acids such as tyrosine, phenylalanine, methionine, and histidine was observed. The accumulation of these large neutral amino acids in the brain was not influenced by 24-hr fasting which caused increases in branched chain amino acids in the serum. From these results, we conclude that the accumulation of the large neutral amino acid in the brain of hyperammonemic state is caused by uptake of ammonia in the brain and the subsequent accumulation of glutamine, but is not influenced by a decreased ratio of branched chain amino acids to aromatic amino acids in the serum.
对缺乏鸟氨酸转氨甲酰酶（尿素循环中的第二步酶）的稀毛小鼠进行了高氨血症及其与脑病关系的研究。我们比较了无特定病原体（spf）小鼠和对照小鼠血清及脑中的氨基酸浓度。与肝性脑病不同，除了瓜氨酸和精氨酸水平较低外，我们在spf小鼠血清中未发现明显的氨基酸变化。但在spf小鼠脑中，高氨血症期间谷氨酰胺显著增加，同时观察到酪氨酸、苯丙氨酸、蛋氨酸和组氨酸等大量中性氨基酸的积累。脑中这些大量中性氨基酸的积累不受24小时禁食的影响，禁食会导致血清中支链氨基酸增加。从这些结果来看，我们得出结论，高氨血症状态下脑中大量中性氨基酸的积累是由脑中氨的摄取以及随后谷氨酰胺的积累引起的，但不受血清中支链氨基酸与芳香族氨基酸比例降低的影响。
