[Changes in the venous endothelium after acute hemodynamic disorders].

Changes in endothelium of the inferior vena cava have been studied in 1, 2, 3, 5, 7, 9, 20, 30 and 50 days on 42 mature rabbits (6 of them used as the control) survived after orthostatic collapse. Fixation in "suza" fluid, after Carnoy or in the 15% formalin solution with a preliminary ultraviolet irradiation in 0.25% silver nitrate solution are used to reveal the cellular borders. Film preparations are prepared and stained with ferric hematoxylin after Heidenhain. The data obtained are statistically treated using the process approximation by means of calculating the sliding averages. The orthostatic collapse, accompanied with certain changes in hemodynamics produces, after the 2d day, a significant decrease in the arrangement of the cellular layer, development of clearly seen certain destructive and necrobiotic shifts in endothelium which are kept for a long time (50 days--time of observations). Beginning from the 5th--7th days, the restorative reaction takes place according to the cell hyperplasia type (increased mitotic coefficient in endotheliocytes) and hypertrophy (increased nuclear and cellular size, presence of binuclear elements), that reflects some processes of the intracellular renewal. The peculiar feature of the regeneration process is its late development and a prolonged course that depends on duration of the pathological shifts in the tissue. The processes observed in the endothelial layer result in an essential increase in the tissue polymorphism that characterizes its main property--plasticity.