[Ultrastructural alterations of the alveolar walls capillaries by injection of histamine (author's transl)].

Histamine chlorhydrate was intravenously injected to Guinea pigs (7 microgram/kg). Alterations of the alveolar walls capillaries were by electronic microscopy studied 1.5, 12 and 15 minutes after injection. It was observed a rapid dilator effect associated with an opening of the endothelial cells tight junctions, an increasing in the size and turnover of pinocytic vesicles, an enlargement and a loss of homogeneity of the basal membrane and an edema of type I pneumocytes. In the last group of animals, lesions reversibility is characterized by a beginning of closing of endothelial cells junctions and of edema resorption. These morphological findings point out the local effect of histamine on the pulmonary capillary microcirculation and show the decrease of resistance and the increase of permeability of the capillaries.