Broer Y, Lhiaubet A M, Rosselin G, Rostène W
C R Acad Sci III. 1987;304(1):31-6.
In the present study, we describe the specificity and the autoradiographic distribution of insulin binding sites in the rat central nervous system (CNS) after in vitro incubation of brain sections with [125I]-14A insulin. Increasing concentrations of unlabeled insulin produced a dose-dependent inhibition of [125I]-insulin binding which represented 92 +/- 2% displacement with 3 X 10(-5) M, whatever the brain sections tested. Half-maximum inhibition with native insulin was obtained with 2.2 X 10(-9) M, with 10(-7) M proinsulin whereas glucagon had no effect. Under our experimental conditions, no degradation of [125I]-insulin was observed. Autoradiograms obtained by apposition of LKB 3H-Ultrofilm showed a widespread distribution of [125I]-insulin in rat CNS. However, quantitative analysis of the autoradiograms with 10(-10) M of labeled insulin, showed a high number of [125I]-insulin binding sites in the choroid plexus, olfactory areas, in both cerebral and cerebellar cortices, the amygdaloid complex and in the septum. In the hippocampal formation, the dorsal dentate gyrus and various subfields of CA1, CA2 and CA3 were labeled. Moreover, arcuate, dorso- and ventromedial nuclei of the hypothalamus contained high concentrations of [125I]-insulin whereas a low density was observed in the mesencephalon. The metabolic role of insulin in the CNS is supported by the large distribution of insulin binding sites in the rat brain. However, the presence of high affinity binding sites in selective areas involved in perception and integrative processes as well as in the regulation of both feeding behavior and neuroendocrine functions, suggests a neuromodulatory role of insulin in the brain.
在本研究中，我们描述了用[125I]-14A胰岛素对脑切片进行体外孵育后，大鼠中枢神经系统（CNS）中胰岛素结合位点的特异性和放射自显影分布。未标记胰岛素浓度的增加对[125I]-胰岛素结合产生剂量依赖性抑制，无论测试的脑切片如何，3×10(-5)M的未标记胰岛素可产生92±2%的置换。天然胰岛素的半数最大抑制浓度为2.2×10(-9)M，胰岛素原的半数最大抑制浓度为10(-7)M，而胰高血糖素无作用。在我们的实验条件下，未观察到[125I]-胰岛素的降解。通过LKB 3H-Ultrofilm贴合获得的放射自显影片显示[125I]-胰岛素在大鼠中枢神经系统中广泛分布。然而，用10(-10)M标记胰岛素对放射自显影片进行定量分析表明，脉络丛、嗅觉区域、大脑和小脑皮质、杏仁复合体以及隔区中有大量[125I]-胰岛素结合位点。在海马结构中，齿状回背侧以及CA1、CA2和CA3的各个亚区都有标记。此外，下丘脑的弓状核、背内侧核和腹内侧核含有高浓度的[125I]-胰岛素，而中脑的浓度较低。胰岛素在中枢神经系统中的代谢作用得到大鼠脑中胰岛素结合位点广泛分布的支持。然而，在参与感知和整合过程以及调节摄食行为和神经内分泌功能的选择性区域中存在高亲和力结合位点，提示胰岛素在脑中具有神经调节作用。
