Isales C, Macala L J, Rodriguez-Commes J, Gasalla-Herraiz J, Hayslett J P
Department of Internal Medicine, Yale School of Medicine, New Haven, Connecticut 06510, USA.
Biochem Biophys Res Commun. 1997 Feb 3;231(1):156-9. doi: 10.1006/bbrc.1997.6063.
Previous studies showed that insulin stimulation of electrogenic Na+ transport in renal epithelial cells is mediated by a calcium-dependent signal transduction mechanism. The present study was performed to determine whether the insulin-induced increase in intracellular Ca2+ (Cai2+) was mediated by hydrolysis of phosphatidylinositol and release of inositol trisphosphate. Experiments were conducted with cultured A6 cells, derived from Xenopus Laevis, grown on permeable supports. Addition of insulin resulted in 2 to 3 fold increases in inositol trisphosphate and a 50% increase in 1,2 diacylglycerol within 10s, which corresponded to the time-course, previously reported, of insulin stimulated increases in Na+ transport and Cai2+. Further studies showed that aldosterone, previously shown to stimulate an increase in 1,4,5-inositol trisphosphate at onset of the rise in Na+ transport, also increased DAG levels during the initial phase of stimulation of Na+ transport. These studies provide the first evidence that a biological response induced by insulin is mediated by hydrolysis of phosphatidylinositol 4,5-bisphosphate (PIP2) which results in two products, inositol trisphosphate which causes the release of Ca2+ from intracellular stores and 1,2 diacylglycerol. In addition this study provides further support for the proposal that a common signal transduction mechanism mediates electrogenic Na+ transport by multiple agonists.
先前的研究表明，胰岛素对肾上皮细胞中电生性Na⁺转运的刺激是由一种钙依赖性信号转导机制介导的。本研究旨在确定胰岛素诱导的细胞内Ca²⁺（Cai²⁺）增加是否由磷脂酰肌醇的水解和肌醇三磷酸的释放介导。实验使用了在可渗透支持物上生长的、源自非洲爪蟾的培养A6细胞进行。添加胰岛素后，10秒内肌醇三磷酸增加2至3倍，1,2 - 二酰甘油增加50%，这与先前报道的胰岛素刺激Na⁺转运和Cai²⁺增加的时间进程相对应。进一步的研究表明，醛固酮先前被证明在Na⁺转运开始增加时会刺激1,4,5 - 肌醇三磷酸增加，在刺激Na⁺转运的初始阶段也会增加二酰甘油水平。这些研究提供了首个证据，即胰岛素诱导的生物学反应是由磷脂酰肌醇4,5 - 二磷酸（PIP2）的水解介导的，其产生两种产物，即导致Ca²⁺从细胞内储存释放的肌醇三磷酸和1,2 - 二酰甘油。此外，本研究为多种激动剂通过共同信号转导机制介导电生性Na⁺转运这一观点提供了进一步支持。
