Abstract:Microvascular endothelial changes are thought to be a crucial step in the development of hemorrhagic changes in various pathological states. Tissue‐type plasminogen activator (t‐PA) is an endothelium‐derived fibrinolytic mediator which regulates microvascular permeability. In this study, we determined the activity and amount of t‐PA in the biopsy specimens taken from gastric mucosa of patients with gastric ulcers to evaluate endothelial alterations and vascular permeable changes in situ. In addition, to elucidate the relationship between local fibrinolytic disturbance and systemic blood coagulation, several factors such as plasminogen activator inhibitor were also assayed. The results of this investigation revealed that the mucosal t‐PA amount in the active ulcer proved to be 2–3 folds higher than that in healthy controls, however, t‐PA levels in plasma samples showed no remarkable differences among the groups. Increased t‐PA activity appeared to well correlate to the degree of inflammation of gastric mucosa in contrast to t‐PA amount which was still increased in healed ulcer lesion. PAI‐1 in plasma samples from gastric ulcer patients showed a significantly high level as compared with healthy subjects. The present study indicates that t‐PA activation may play an important role in the pathogenesis of gastric ulcer formation and that t‐PA determination in gastric biopsy specimens may be useful for the evaluation of clinical activity of gastric ulcers in terms of the mucosal microvascu