Myo-inositol does not modulate PI turnover in MDCK cells under hyperosmolar conditions.
Myo-inositol does not modulate PI turnover in MDCK cells under hyperosmolar conditions.
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在高渗条件下，肌醇不调节 MDCK 细胞的 PI 转换。
DOI：
10.1152/ajprenal.1990.258.5.f1282
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发表时间：
1990
期刊：
影响因子：
--
通讯作者：
Wu,D
中科院分区：
文献类型：
--
作者：
Shayman,JA;Wu,D
在等渗和高渗条件下，研究了Madin-Darby犬肾（MDCK）细胞中游离细胞肌醇浓度与磷脂酰肌醇转化的关系。暴露于高细胞外氯化钠的MDCK细胞被记录为增加其游离肌醇含量，通过气液色谱法以时间和浓度依赖的方式测量。测量磷脂酰肌醇、磷脂酰肌醇4-单磷酸和磷脂酰肌醇4,5-二磷酸的质量未能揭示肌醇浓度比对照条件高出三倍以上的条件下的变化。在控制和高渗透压条件下生长的MDCK细胞的质膜中测量的CDP二酰基甘油：肌醇3-磷脂酰转移酶活性与观察到的Michaelis常数（Km）和最大酶反应速率在动力学上相似。此外，表观Km明显低于估计的细胞内肌醇浓度，这与两种情况下转移酶暴露于饱和肌醇浓度一致。最后，用竞争结合法测定缓激肽刺激的肌醇三磷酸质量。在控制和高渗条件下，基础和激素刺激的肌醇1,4,5-三磷酸水平没有显著差异。这些数据表明，在高渗条件下，散装游离肌醇含量不太可能调节磷脂酰肌醇的转化和肌醇三磷酸的形成。
The relationship between free cellular myo-inositol concentration and phosphatidylinositol turnover was evaluated in Madin-Darby canine kidney (MDCK) cells under isosmolar and hyperosmolar conditions. MDCK cells exposed to high extracellular sodium chloride were documented to increase their free myo-inositol content as measured by gas-liquid chromatography in both a time- and concentration-dependent manner. Measurement of phosphatidylinositol, phosphatidylinositol 4-monophosphate, and phosphatidylinositol 4,5-bisphosphate mass failed to reveal changes under conditions where the myo-inositol concentration was more than threefold higher compared with control conditions. CDP diacylglycerol:myo-inositol 3-phosphatidyltransferase activity, measured in plasma membranes from MDCK cells grown under control and hyperosmolar conditions, was kinetically similar with comparable observed Michaelis constant (Km) and maximal rate of enzyme reaction. Moreover, the apparent Km was significantly below the estimated intracellular myo-inositol concentration consistent with exposure of the transferase to saturating concentrations of myo-inositol under both conditions. Finally, bradykinin-stimulated myo-inositol trisphosphate mass was measured by use of a competitive binding assay. Both basal and hormone-stimulated myo-inositol 1,4,5-trisphosphate levels were not significantly different under control and hyperosmolar conditions. These data indicate that bulk free myo-inositol content is unlikely to regulate phosphatidylinositol turnover and myo-inositol trisphosphate formation under hyperosmolar conditions.