[Characteristics of the ultrastructural organization of endothelial cells in cardiac and omental blood capillaries based on cryofractographic data].

Using cryofractography, endotheliocytes of heart and omentum blood capillaries were studied, different patterns of distribution of membranous particles being observed of the "P" and "E" faces of the fracture plans of endothelial cell cytomembranes. Three types of distribution of micropinocytotic vesicles can be distinguished: the linear, hexagonal, and the clusteral type. The number of micropinocytotic vesicles was sharply reduced near the region of intercellular contacts. On the fracture plan, attached pinocytotic vesicles look like "craters" on the "E" face, and like circumvallatue papillae on the "P" face. Cell membranes, making intercellular contacts, have a network structure consisting of ridges on the "P" face and of grooves on the "E" face. Such a molecular membrane organization is discussed from the standpoint of modern concepts of the receptor--cytosceletal complex. It is supposed that this complex may control processes of transendothelial mass--transfer.