Kato T, Sano M, Mizutani N
Eur J Pediatr. 1987 Jan;146(1):56-8. doi: 10.1007/BF00647285.
Intravenous infusion of 0.5 mmol/kg L-lysine monohydrochloride was performed in six normal volunteer subjects aged 10-14 years to study the inhibitory effect of lysine on urea cycle metabolism. The lysine infusion resulted in a significant increase in plasma levels of arginine and ornithine, and in urinary homocitrulline, putrescine, and orotic acid, accompanied by a significant increase in blood ammonia. There was little change in plasma urea and citrulline. The increase in plasma arginine appears to reflect an inhibited arginase activity although the plasma urea level did not change. The increased homocitrulline excretion suggests that ornithine conversion to citrulline via ornithine transcarbamylase (OTC) was inhibited. The simultaneous increase in plasma ornithine and urinary putrescine may reflect an inhibition of mitochondrial ornithine transport. In addition to the direct ammoniagenic property of lysine, impaired ornithine conversion to citrulline resulting from the inhibition of both OTC activity and mitochondrial ornithine uptake by lysine may be responsible for the increase in blood ammonia and urinary orotic acid. Despite the retarded citrulline formation, a promoted efflux of citrulline from mitochondria may have kept the plasma citrulline level unchanged.
对6名年龄在10至14岁的正常志愿者进行静脉输注0.5 mmol/kg的L-赖氨酸单盐酸盐，以研究赖氨酸对尿素循环代谢的抑制作用。输注赖氨酸导致血浆中精氨酸和鸟氨酸水平显著升高，尿中同型瓜氨酸、腐胺和乳清酸水平显著升高，同时血氨也显著升高。血浆尿素和瓜氨酸变化不大。血浆精氨酸的升高似乎反映了精氨酸酶活性受到抑制，尽管血浆尿素水平没有变化。同型瓜氨酸排泄增加表明鸟氨酸通过鸟氨酸转氨甲酰酶（OTC）转化为瓜氨酸的过程受到抑制。血浆鸟氨酸和尿腐胺同时升高可能反映了线粒体鸟氨酸转运受到抑制。除了赖氨酸直接的产氨特性外，赖氨酸抑制OTC活性和线粒体鸟氨酸摄取导致鸟氨酸转化为瓜氨酸受损，可能是血氨和尿乳清酸增加的原因。尽管瓜氨酸形成受阻，但线粒体中瓜氨酸流出增加可能使血浆瓜氨酸水平保持不变。
