Hemostatic Mechanisms, Independent of Platelet Aggregation, Arrest Gastric Mucosal Bleeding

Platelet adhesion, aggregation, and subsequent plug formation play a major role in the control of cutaneous and vascular hemostasis. Little is known, however, about the hemostatic processes in gastric mucosal tissue. A method for evaluating bleeding from a standard incision in the gastric mucosa of the rat, rabbit, and dog has therefore been developed. By using pharmacological agents that interfere with platelet aggregation and blood coagulation, the mechanism of gastric hemostasis has been compared to that in the vasculature, using the rat mesenteric artery. Intravenous infusion of prostacyclin (0.5 μ g· kg-1· min-1), which inhibits platelet aggregation directly, or administration of the thromboxane synthase inhibitor 1-benzylimidazole (50 mg· kg-1) significantly prolonged bleeding in the mesenteric artery yet failed to alter gastric mucosal bleeding. In contrast, a low dose of heparin (100 units· kg-1), which interferes with the clotting process, had no effect on mesenteric bleeding but substantially prolonged bleeding from the gastric mucosa. These findings suggest that, unlike in the skin or vasculature, platelet aggregation plays a minimal role in the initial hemostatic events in the gastric mucosa and that the arrest of gastric hemorrhage is brought about largely by processes primarily involving the coagulation system.