Watford M
Department of Nutritional Sciences, Cook College, Rutgers University, New Brunswick, NJ, USA.
J Nutr. 2000 Apr;130(4S Suppl):983S-7S. doi: 10.1093/jn/130.4.983S.
The liver shows net glutamine uptake after a protein-containing meal, during uncontrolled diabetes, sepsis and short-term starvation, but changes to net release during long-term starvation and metabolic acidosis. Some studies report a small net release of glutamate by the liver. The differential expression of glutamine synthetase (perivenous) and glutaminase (periportal) within the liver indicates that glutamine is used for urea synthesis in periportal cells, whereas glutamine synthesis serves to detoxify any residual ammonia in perivenous cells. Experiments in vivo suggest that changes in net hepatic glutamine balance are due predominantly to regulation of glutaminase activity, with the flux through glutamine synthetase being relatively constant.
在摄入含蛋白质的餐后、未控制的糖尿病期间、脓毒症期间以及短期饥饿时，肝脏表现为净摄取谷氨酰胺，但在长期饥饿和代谢性酸中毒时则转变为净释放。一些研究报告称肝脏有少量谷氨酸的净释放。肝脏内谷氨酰胺合成酶（小叶静脉周围）和谷氨酰胺酶（门静脉周围）的差异表达表明，谷氨酰胺在门静脉周围细胞中用于尿素合成，而谷氨酰胺合成则用于清除小叶静脉周围细胞中任何残留的氨。体内实验表明，肝脏谷氨酰胺净平衡的变化主要归因于谷氨酰胺酶活性的调节，而通过谷氨酰胺合成酶的通量相对恒定。
