Endothelial and perivascular anionic sites during immediate transient vascular leakage

To study surface charge characteristics of small blood vessels and perivascular components in vivo, rat cremaster vessels exposed to serotonin or mild thermal injury were labelled with systemically injected cationized ferritin and studied by electron microscopy. Leaky vessels showed increased density of anionic sites on the luminal endothelial plasma membrane, compared to controls. Binding of cationized ferritin and the increased density of anionic sites in leaky vessels occurred in the absence of serum factors; albumin diminished both phenomena. Anionic sites were also demonstrated a) on the surface membranes of open interendothelial junctions, b) on the attachment surface of endothelial cells, c) along the vascular basal lamina, perimysial membrane, and interstitial collagen. The biological significance of these findings is considered in relation to ligand-anionic sites interaction, inflammation, vascular permeability, and thrombosis.