Abstract
Perfusion of the fenestrated capillaries of the intestinal mucosa of the rat with 0.05-0.1 M EDTA removes the diaphragms of the endothelial cells and detaches these cells from one another and from the basement membrane. The latter, even when completely denuded, retains effectively particles of 340 A (average) diameter. Perfusion with histamine (1 microg/ml) results in partial removal of fenestral diaphragms, occasional detachment of the endothelium from the basement membrane, and focal separation of endothelial intercellular junctions.