Regulation of flow‐induced intracellular NO levels by endothelial surface glycocalyx

Abstract

To test the hypothesis that endothelial surface glycocalyx (ESG) plays a role in mechanosensing and transduction of the microvessel wall, we used fluorescence microscopy to measure the NO levels in the post‐capillary venules of rat mesentery under low and high flow conditions and with/out enzyme treatment for removing heparan sulfate (HS) of the ESG. Rats (SD, 250–300g) were anesthetized with pentobarbital sodium given subcutaneously, the mesentery was gently taken out from the abdominal cavity and arranged on the surface of a glass coverslip for the measurement. After perfusion for 1 hr with 1% BSA Ringer for the control or with 50 mU/mL heparanase III for the treatment, an individual post‐capillary venule (35–50 μm) was loaded for 45 min with 5 μM 4, 5‐Diaminofluorescein diacetate, a membrane permeable fluorescent indictor for NO, then the NO was measured for ~10min under a low flow (< 300 μm/s) as the baseline and for ~60min under a high flow (1500–2000 μm/s mean velocity). In 1 min after switching to the high low, NO increased by 1.14 ± 0.05‐fold (n=3) under control and 1.15 ± 0.04‐fold (n=3) under enzyme treatment. NO continuously increased after 1 min under high flow, reached a plateau of 1.42 ± 0.02‐fold in ~40 min under control and of 1.22 ± 0.03 in ~15min under treatment. The results suggest that ESG participate in EC mechanosensing and transduction through its HS and other components. Supported by NIH R01HL094889–01.