渗透压对血管内皮细胞中NO合成酶活性的影响及其机制研究

目的：研究非等渗压浓度对血管内皮细胞NO合成酶活性的影响,并探索其发生机制。方法：使血管内皮细胞暴露于低渗（205mOsm)或高渗透压（410mOsm)培养液,用Griess法测定NO合成酶（NOS）活性,以Northern blot ting观测细胞iNOS和eNOS基因表达的变化。结果： 非等渗压浓度可使血管内皮细胞中NOS活性显著升高。细胞NOS活性变化具有明显的时间效应规律,低渗透压浓度效应产生的效应早于高渗透压浓度,且低渗透压浓度的影响较高渗透压浓度更为明显。Dexamethasone对这种非等渗透压诱导的NOS活性没有明显作用,给予cycloheximide,不影响非等渗压诱导的这种差异。Nothern blot分析表明：非等渗压浓度不诱导iNOS基因表达,而使eNOSmRNA表达增加。结论：非等渗透压浓度诱导血管内皮细胞NOS活性升高,eNOS基因表达增强是其主要机制之一。

Effects of osmolarity on NO synthase activity in endothelial cells and its mechanism

Aim: To investigate the effects of the osmolarity on the NO synthase (NOS) activity in endothelial cells and explore their mechanism. Methods: The endothelial cells were exposed to hypotonic(205 mOsm) or hypertonic(410mOslm) in culture medium. Griess assay was used to measure NOS activity in cells. The inducible NOS(iNOS) and endothelial NOS(eNOS) gene expression were detected by Norhern blot method. Results: After exposed to hypotonic or hypertonic medium NOS activity of eEND cells increased significantly compared with that of endothelial cells cultured in isotonic medium(305 mOsm). The increases induced by non isotonic changed in time dependent model. The effect of hypotonic on NOS activity was more significant than that of hypertonic. Dexamethasone had no effect on the increases of NOS activity induced by non isotonic osmolarity. Cycloheximide supressed NOS activity via in hibiting protein synthesis but in cycloheximide treated cells,but hypotonic or hypertonic still caused significant increase in NOS activity over the control. The results of Northern blot analysis showed that hypotonic and hypertonic induced the increase of eNOS gene expression, but had no effect on iNOS gene. Conclusion: Hypotonic and hypertonic specifically increased eNOS activity in endothelial cells, in which the increase of eNOS gene expression may play an important role.