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T.E. Walshe, P.P. Connell, C.J. O'Brien, P. Cahill; Pulsatile Flow Regulates Endothelial Nitric Oxide Synthase Expression in Co-Cultured Retinal Endothelial & Pericyte Cells . Invest. Ophthalmol. Vis. Sci. 2003;44(13):139.
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© ARVO (1962-2015); The Authors (2016-present)
Purpose: Nitric Oxide (NO) is responsible for relaxation of pericytes in the microvasculature. It has been proposed that retinal blood flow autoregulation is impaired in pathologies associated with Normal Tension Glaucoma, as a result of some inherent endotheliopathy. As hemodynamic forces have been shown to have a profound influence on endothelium-mediated events, we hypothesize that expression and function of phosphorylated Nitric Oxide Synthase (pp-eNOS), is regulated by shear stress. Methods: We examined the effect of shear stress on pp-eNOS expression and activity in a perfused transcapillary co-culture system(Cellmax Quad Artificial Capillary Cell Culture System). Mono cultures of bovine retinal endothelial cells (BRECs) and co-cultures of BRECs with bovine retinal pericytes were exposed to low flow (0.3 mls/min) and high flow (25 mls/min) for 24 hours. Cells were harvested for western blot analysis, and media samples were analysed for changes in nitrite using a fluorometric assay (DAN). Results: In mono-culture of BRECs, we found a 1.96 ± 0.49 (n=2) fold increase in pp-eNOS protein expression and a 2.61 ± 0.37 (n=2) fold increase in nitrite levels from low to high pulsatile flow. In co-culture, we found a 2.50 fold increase in pp-eNOS protein expression from low to high flow and a 2.54 fold increase in nitrite levels. Conclusion: These results demonstrate that shear stress can modulate retinal vessel diameter, as NO is a potent dilator of retinal pericytes.
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