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Effects of vascular endothelial growth factor (VEGF) and angiotensin II (Ang II) on endothelial nano‐channels

The juxtaglomerular portion of afferent arteriole (AA) is fenestrated and these nano‐channels may serve as a pathway for the renin into the circulation. VEGF and Ang II were examined as possible regulators of the formation of endothelial fenestration in human umbilical vein endothelial cell culture. Atomic force microscopy (AFM) was used to study the morphology of the fenestrae and dynamism of its appearance. Permeability of the endothelial monolayer, as a functional indication of fenestration was measured using 40 kDa FITC‐labeled dextran. With AFM 12.1±2.5 fenestrae/8x8 μm field of the endothelial cell surface were observed. About 90 percent of fenestrae had diameter less than 200 nm. The opening of individual fenestrae showed gyrus‐like upfolding. Measurements revealed funnel shaped nano‐channels. 48 hours treatments with both Ang II (10−7 M) and VEGF (100 ng/ml) induced significant increases in the number of channels. Ang II significantly increased endothelial permeability too. The permeability increasing effects of VEGF were more pronounced and appeared within 15 minutes. In summary we have visualized and characterized the individual endothelial nano‐channel utilizing the AFM. In addition we have demonstrated that Ang II and VEGF increase the number of fenestrae and the permeability of the HUVEC monolayer, therefore both agents could be important regulators of endothelial fenestration in the AA.