Durschlag R P, Smith R J
Am J Physiol. 1985 May;248(5 Pt 1):C442-8. doi: 10.1152/ajpcell.1985.248.5.C442.
Cells of the L6 rat myogenic line consume glutamine in contrast to skeletal muscle in vivo, which produces glutamine. The basis of glutamine consumption in the cultured cells and the conditions under which net glutamine production occurs were investigated. After treating cultures with cytosine-1-beta-D-arabinofuranoside to eliminate replicating myoblasts remaining after differentiation, the L6 cells continued to consume glutamine from medium containing normal plasma levels (650 microM). Consumption declined when cells were incubated with 325 microM glutamine, and, at 0 microM, net production occurred. In addition to the tendency to consume glutamine, the cells rapidly consumed glutamic acid. When medium glutamic acid was increased from 70 to 150, 500, and 1,000 microM, glutamine production increased. Alterations in levels of NH3, the other substrate for glutamine synthesis, did not have this effect. The L6 cells were found to have glutamine synthetase activity similar to normal rat skeletal muscle but markedly increased glutaminase activity. In spite of the imbalance in synthetic and degradative activities, however, inhibitor studies with L-methionine sulfoximine and 6-diazo-5-oxo-L-norleucine showed that flux through both pathways influenced net glutamine production.
与体内产生谷氨酰胺的骨骼肌不同，L6大鼠成肌细胞系的细胞消耗谷氨酰胺。研究了培养细胞中谷氨酰胺消耗的基础以及发生净谷氨酰胺产生的条件。在用胞嘧啶-1-β-D-阿拉伯呋喃糖苷处理培养物以消除分化后残留的增殖成肌细胞后，L6细胞继续从含有正常血浆水平（650微摩尔）的培养基中消耗谷氨酰胺。当细胞与325微摩尔谷氨酰胺一起孵育时，消耗量下降，而在0微摩尔时，发生净产生。除了有消耗谷氨酰胺的倾向外，这些细胞还迅速消耗谷氨酸。当培养基中的谷氨酸从70微摩尔增加到150、500和1000微摩尔时，谷氨酰胺的产生增加。谷氨酰胺合成的另一种底物NH3水平的改变没有这种作用。发现L6细胞具有与正常大鼠骨骼肌相似的谷氨酰胺合成酶活性，但谷氨酰胺酶活性明显增加。然而，尽管合成和降解活性不平衡，但用L-甲硫氨酸亚砜亚胺和6-重氮-5-氧代-L-正亮氨酸进行的抑制剂研究表明，两条途径的通量都影响净谷氨酰胺的产生。
