Uptake and inactivation of thrombin on aortic endothelium and neo-intima

The aim of this study was to investigate the uptake and inactivation of thrombin on aortic endothelium and neo-intima developing on vascular grafts in pigs and dogs. Thrombin, measured with a synthetic chromogenic substrate, was found on the grafts, particularly on grafts with an incompletely developed neo-intima. After incubation of grafts and aortic segments with thrombin in vitro, significantly more thrombin was taken up on the grafts as compared to aortic endothelium. In the presence of plasma, surface-bound thrombin was inactivated much faster on aortic endothelium than on neo-intima. If surfaces loaded with thrombin in vitro were incubated with a balanced salt solution the enzyme was inhibited much more slowly. Thrombin activity on the neo-intima may contribute to graft thrombosis.