Shah B H, Hausman R E
Department of Biology, Boston University, MA 02215.
Brain Res Dev Brain Res. 1993 Apr 16;72(2):151-8. doi: 10.1016/0165-3806(93)90180-i.
We investigated the role of insulin in GABAergic differentiation in the embryonic chick retina at different embryonic ages using glutamate decarboxylase (GAD) and high-affinity GABA uptake as developmental markers. Both these GABAergic markers exhibit developmentally programmed increases in activity during retinogenesis that also occur in culture. Insulin stimulated GABA uptake in retina neurons at all embryonic ages in a dose-dependent manner and GAD activity by 30% in embryonic retina neurons after 11 days of development. The stimulation of GABA uptake by insulin was blocked by addition of ouabain suggesting a role for the Na+,K+ ATPase. The same concentration of insulin caused a 76% stimulation of protein synthesis in these retinal cells, and previous work demonstrated that insulin also stimulates cholinergic differentiation in the chick retina (Hausman et al., Dev. Brain. Res. 59, (1991) 31-37). Thus, there was no selective stimulation of GABAergic differentiation by insulin but likely a neurotrophic effect. The increase in GAD activity in neurons from post-11-day embryonic neurons contrasts with our previous findings at embryonic days 6-7 where there is little change in GAD activity after addition of insulin. It is possible that the failure of insulin to stimulate GAD activity during early retina development is due to the increased accumulation of GABA in the presence of insulin. GABA levels were increased more than two-fold by 100 ng/ml insulin.
我们使用谷氨酸脱羧酶（GAD）和高亲和力GABA摄取作为发育标志物，研究了胰岛素在不同胚胎时期的鸡胚视网膜GABA能分化中的作用。这两种GABA能标志物在视网膜发生过程中均表现出发育程序控制的活性增加，在培养中也会出现这种情况。胰岛素在所有胚胎时期均以剂量依赖性方式刺激视网膜神经元摄取GABA，并在发育11天后使胚胎视网膜神经元的GAD活性提高30%。哇巴因的加入可阻断胰岛素对GABA摄取的刺激作用，提示Na +,K + ATP酶发挥了作用。相同浓度的胰岛素使这些视网膜细胞中的蛋白质合成增加了76%，并且先前的研究表明胰岛素还能刺激鸡胚视网膜中的胆碱能分化（Hausman等人，《发育脑研究》59，（1991）31 - 37）。因此，胰岛素并非选择性地刺激GABA能分化，而可能具有神经营养作用。11天龄后胚胎神经元中GAD活性的增加与我们之前在胚胎第6 - 7天的研究结果形成对比，当时加入胰岛素后GAD活性几乎没有变化。胰岛素在视网膜早期发育过程中未能刺激GAD活性，可能是由于在胰岛素存在的情况下GABA积累增加所致。100 ng/ml胰岛素使GABA水平增加了两倍多。
