[Ultrastructural changes in the wall of the inferior vena cava following acute obstruction of venous drainage].

Ultrastructure of the abdominal part of rat vena cava posterior was studied over a period of 2 to 20 hours after acute failure of blood outflow. This disturbance was induced by vein coarctation with a silk ligature. During the first two hours and afterwards, alteration and desquamation of the endothelium were observed. 16--20 hours after vein coarctation there occurred degeneration of some smooth muscle cells and transitory migration of blood monocytes to the vein wall. Platelet aggregations could be seen rarely. Intimal fibromuscular thickenings reported in previous papers were located at the most severely affected sites of the endothelium. The data obtained confirm the hypothesis of the presence of endothelial muscle interactions.