Circulating proteins and macromolecular transport across continuous, nonfenestrated endothelium.

Experiments are described, using isolated perfused capillaries, fluorocarbon exchanged rats, and endothelial cells in culture, that examine the interaction of circulating proteins with the endothelial surface. A consequence of the interaction of circulating proteins with the endothelial surface is to render the endothelium less permeable to water, small water-soluble molecules, as well as macromolecules. Indirect evidence suggests that this is the result of adsorption of proteins to the glycoprotein coat of endothelial cells. An understanding of the physiochemical basis for this interaction awaits further studies of the chemical composition and properties of molecules constituting the endothelial cell surface.