[Action of histamine on the aortic endothelium]

Changes of the shape and surface of aortal endotheliocytes under the effect of histamine were studied by scanning electron microscopy. Incubation of fragments of the aorta in a histamine solution for 1 min results in changes of the nucleus-containing zone of some portion of the endotheliocytes into a spindle shape. The surface of the peripheral zone was characterized by the presence of spherical swellings. In some parts of the marginal zones of the cells there were numerous stomata of various sizes. Incubation of aorta for 5 min resulted in considerable alterations in the endotheliocyte stereoultrastructure. The nucleus- containing zones strongly protruded into the lumen. The cells became spherical. The peripheral zone was perforated by numerous stomata. The cell edges separated markedly at contact sites. The results suggest that the mechanism of the observed changes in the shape and surface of the cells may be associated with activation of the cytoskeletic complex (microtubules, microfilaments) under the effect of histamine.