Scott W N, Slatin S L, Cobb M H, Reich I M
Endocrinology. 1981 Nov;109(5):1775-7. doi: 10.1210/endo-109-5-1775.
Insulin-stimulated sodium transport in the toad urinary bladder consists of two components, a brief element of rapid onset that is independent of protein synthesis, and a sustained increase, slower in onset, that is dependent upon RNA and protein synthesis. The mucosal epithelium of the toad bladder was labeled by lactoperoxidase-catalyzed radioiodination (125I) following 15 min and 3 h exposure to insulin. The membrane of "mitochondria-rich" and "granular" mucosal cells from these tissues were analyzed by electrophoresis in SDS-urea. Compared to untreated tissues, membranes of "granular" mucosal cells from tissues exposed to insulin for 15 min contained a band (Mr = 15,000) with significantly increased labeling. Bladders exposed to insulin for 3 h showed no consistent increase in labeling. These data suggest that there are differences in the conformation of apical membrane proteins during the two phases of hormone-induced sodium transport. The technique may also offer an opportunity to identify "effector" proteins mediating this and other insulin responses.
胰岛素刺激蟾蜍膀胱的钠转运由两个部分组成，一个是快速起效的短暂成分，它不依赖蛋白质合成，另一个是起效较慢的持续增加成分，它依赖RNA和蛋白质合成。在暴露于胰岛素15分钟和3小时后，通过乳过氧化物酶催化的放射性碘化（125I）对蟾蜍膀胱的黏膜上皮进行标记。对这些组织中“富含线粒体”和“颗粒状”黏膜细胞的膜进行SDS-尿素电泳分析。与未处理的组织相比，暴露于胰岛素15分钟的组织中“颗粒状”黏膜细胞的膜含有一条带（Mr = 15,000），其标记显著增加。暴露于胰岛素3小时的膀胱在标记上没有一致的增加。这些数据表明，在激素诱导的钠转运的两个阶段，顶端膜蛋白的构象存在差异。该技术还可能提供一个机会来鉴定介导这种和其他胰岛素反应的“效应器”蛋白。
