科研之友
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摘要
Due to its unique location, the endothelial surface glycocalyx ( ESG) at the luminal side of the microvessel wall may serve as a mechano-sensor and transducer of blood flow and thus regulate endothelial functions. To examine this role of the ESG, we used fluorescence microscopy to measure nitric oxide ( NO) production in post-capillary venules and arterioles of rat mesentery under reduced ( low) and normal ( high) flow conditions, with and without enzyme pretreatment to remove heparan sulfate ( HS) of the ESG and in the presence of an endothelial nitric oxide synthase ( eNOS) inhibitor, N-G-monomethyl-L-arginine ( L-NMMA). Rats ( SD, 250-300g) were anesthetized. The mesentery was gently taken out from the abdominal cavity and arranged on the surface of a glass coverslip for the measurement. An individual post-capillary venule or arteriole was cannulated and loaded for 45 min with 5 mu M 4, 5-Diaminofluorescein diacetate, a membrane permeable fluorescent indictor for NO, then the NO production was measured for similar to 10 min under a low flow (similar to 300 mu m/s) and for similar to 60 min under a high flow (similar to 1000 mu m/s). In the 15 min after switching to the high flow, DAF-2-NO fluorescence intensity increased to 1.27-fold of its baseline, DAF-2-NO continuously increased under the high flow, to 1.53-fold of its baseline in 60 min. Inhibition of eNOS by 1 mM L-NMMA attenuated the flow-induced NO production to 1.13-fold in 15 min and 1.30-fold of its baseline in 60 min, respectively. In contrast, no significant increase in NO production was observed after switching to the high flow for 60 min when 1 h pretreatment with 50 mU/mL heparanase III to degrade the ESG was applied. Similar NO production was observed in arterioles under low and high flows and under eNOS inhibition. Our results suggest that ESG participates in endothelial cell mechanosensing and transduction through its heparan sulfate to activate eNOS.
- 出版日期2015-1-9
