The effect of heparin on stress ulcer formation in rats.

The effect of heparin on acute gastric hemorrhagic lesions in rats induced by cold restraint stress was examined in relation to dose responsiveness. Prestress heparin with intravenous injection of either 50 or 500 U/Kg significantly reduced gastric bleeding (P less than 0.01). Treatment with the former dose inhibited the formation of gastric ulceration (P less than 0.01). Heparin poststress with both doses did not significantly affect either gastric bleeding or ulceration. In contrast, both heparin prestress and poststress at 5000 U/Kg intravenously markedly enhanced gastric bleeding (P less than 0.05 and P less than 0.01, respectively). The results encourage the use of low-heparin prophylaxis for stress ulcers in patients at high risk, and support the concept of a thrombotic etiology for this disease.