Biochemical studies of isolated glial (muller) cells from the turtle retina
Biochemical studies of isolated glial (muller) cells from the turtle retina
复制标题
从海龟视网膜中分离出的神经胶质（穆勒）细胞的生化研究
作者：
P. Sarthy;D. Lam
本文报道了一种从海龟视网膜中分离大量神经胶质细胞的方法。在视网膜的蛋白水解解离后，通过单位重力下的速度沉降将Muller细胞与视网膜神经元分离。通过该方法制备含有> 90%形态学上可识别的Muller细胞的级分。通过在目视观察下将选择的细胞单独吸入微量移液器中，获得仅含有Muller细胞的级分。分离的Muller细胞的生化分析表明：（a）当与适当的放射性前体孵育时，这些细胞不合成和积累乙酰胆碱、γ-氨基丁酸或儿茶酚胺;（B）这些细胞中胆碱乙酰转移酶（EC 2.3.1.6）、谷氨酸脱羧酶（EC 4.1.1.15）和酪氨酸羟化酶（EC 1.14.16.2）的比活性小于视网膜中发现的比活性的2%;（c）然而，Muller细胞含有高活性的递质降解酶-乙酰胆碱酯酶（EC 3.1.1.7）和γ-氨基丁酸-转氨酶（EC 2.6.1.19）;（d）细胞还具有高水平的两种可能是胶质细胞特异性的酶-谷氨酰胺合成酶（EC 6.3.1.2）和碳酸酐酶（EC 4.2.1.1）。这些结果与其他发现一起表明，Muller细胞不能合成神经递质，但具有在视网膜中发挥两个重要作用所必需的酶：（a）突触传递后某些递质通过摄取和降解而失活，及（B）维持酸-碱平衡以及通过去除二氧化碳和氨等代谢产物在视网膜中提供稳定的微环境。
A method has been developed for the preparation of large numbers of glial (Muller) cells from the turtle retina. After proteolytic dissociation of the retina, Muller cells were separated from retinal neurons by velocity sedimentation at unit gravity. Fractions containing >90 percent morphologically identifiable Muller cells were prepared by this procedure. Fractions containing only Muller cells were obtained by drawing selected cells individually into a micropipette under visual observation. Biochemical analyses of isolated Muller cells showed that (a) these cells did not synthesize and accumulate acetylcholine, γ-aminobutyric acid, or catecholamines when incubated with appropriate radioactive precursors; (b) the specific activities of choline acetyltransferase (EC 2.3.1.6), glutamate decarboxylase (EC 4.1.1.15), and tyrosine hydroxylase (EC 1.14.16.2) in these cells were less than 2 percent of those found in the retina; (c) Muller cells, however, contained high activities of transmitter degrading enzymes-acetylcholinesterase (EC 3.1.1.7) and γ-aminobutyrate- transamine (EC 2.6.1.19); and (d) the cells also possessed high levels of two presumably glial-specific-enzymes-glutamine synthetase (EC 6.3.1.2) and carbonic anhydrase (EC 4.2.1.1). These results, together with other findings, suggest that Muller cells are not capable of neurotransmitter syntheses but possess the enzymes necessary for two important roles in the retina: (a) the inactivation of certain transmitters after synaptic transmission by uptake and degradation, and (b) the maintenance of acid-base balance and the provision of a stable microenvironment in the retina by the removal of metabolic products such as carbon dioxide and ammonia.