Anionic fixed charges in the fenestrated capillaries of the mouse mesentery

Previous studies showed the existence of submesothelial fenestrated capillaries in the human parietal and rabbit diaphragmatic peritoneum, as well as in the mouse mesentery. The present study demonstrates the presence of electronegative fixed charges at the luminal aspect of endothelial cells, as well as long the subendothelial basement membrane of the fenestrated capillaries of the mouse mesentery. This situation will eventually preclude the transfenestral passage of anionic plasma proteins. On the other hand, fenestrated capillaries are much more permeable to water and small-molecular-size solutes than those of the continuous type. Therefore, the high hydraulic conductivity of fenestrae may well imply that a substantial part of water and small solutes leave the blood compartment through the fenestral channels.