Endothelial fibrinolysis and ultrastructure following graded mechanical trauma

For study of the progression and resolution of endothelial damage following mechanical vascular trauma in rats, the effects of a clamp with hydrostatically controlled occlusion pressure were compared with those of a standard mechanical clamp. The endothelial morphology was investigated with scanning electron microscopy and its function with histochemical analysis of plasminogen activator activity. Arterial or venous compression with hydrostatic pressure 1.5 kPa (11 mmHg) for 5 or 20 min produced de-endothelialized areas in veins, but only slight endothelial elevation in arteries. Hydrostatic occlusion of arteries with 12 kPa (90 mmHg) for 30 sec did not affect endothelial morphology and fibrinolytic activity, but after occlusion for 5 or 20 min the endothelium in both arteries and veins was severely damaged. The effects of hydrostatic (12 kPa) clamping on endothelial morphology and function after 5 or 20 min did not differ from those of mechanical (48 kPa = 360 mmHg) clamping. Apposition of vascular walls, except for the shortest time (30 sec) thus injured the endothelium, but minimizing occlusion pressure may reduce structural damage in the vessel wall.