Ali S, Bassett J R
School of Biological Sciences, Macquarie University, NSW, Australia.
J Steroid Biochem Mol Biol. 1991 Jul;39(1):119-29. doi: 10.1016/0960-0760(91)90020-6.
Stimulation of incubated rat adrenal slices with ACTH(1-24) resulted in an increase in the release of both corticosterone and specific corticosterone-binding protein into the incubation medium. The release of corticosterone and binding protein was dose and calcium dependent with adrenals from animals pretreated with betamethasone. While the secretion of corticosterone was continuous throughout the incubation period, there appeared to be a limit to the increase in binding capacity. The specificity of steroid binding to the adrenal protein showed a similar profile to that of corticosteroid-binding globulin (CBG) in rat serum. A Western blot analysis using anti-rat CBG as the primary antiserum, showed that the adrenal protein was not CBG. [3H]corticosterone binding with disc electrophoresis, run at 2 degrees C, gave a single peak with approximately the same Rf value for rat serum, purified CBG, and adrenal incubate; at 22 degrees C peaks were only seen for rat serum or purified CBG. The data presented provides further evidence for the existence of a specific corticosterone-binding protein of adrenal origin released in conjunction with corticosterone. The adrenal protein would appear to have a lower affinity for corticosterone than does CBG, and to be functionally more labile. It is possible that the adrenal protein may be CBG that has been internalized, modified and released with corticosterone.
用促肾上腺皮质激素（1 - 24）刺激孵育的大鼠肾上腺切片，导致皮质酮和特异性皮质酮结合蛋白释放到孵育培养基中的量增加。对于用倍他米松预处理的动物的肾上腺，皮质酮和结合蛋白的释放呈剂量和钙依赖性。虽然在整个孵育期间皮质酮的分泌是持续的，但结合能力的增加似乎存在一个限度。类固醇与肾上腺蛋白结合的特异性显示出与大鼠血清中皮质类固醇结合球蛋白（CBG）相似的特征。使用抗大鼠CBG作为一抗的蛋白质免疫印迹分析表明，肾上腺蛋白不是CBG。在2℃下进行圆盘电泳时，[3H]皮质酮结合显示大鼠血清、纯化的CBG和肾上腺孵育物有一个单一峰，其相对迁移率（Rf）值大致相同；在22℃时，仅在大鼠血清或纯化的CBG中出现峰。所提供的数据进一步证明存在一种与皮质酮一起释放的肾上腺来源的特异性皮质酮结合蛋白。肾上腺蛋白对皮质酮的亲和力似乎比CBG低，并且在功能上更不稳定。肾上腺蛋白有可能是被内化、修饰并与皮质酮一起释放的CBG。
