Neutrophil accumulation in development of gastric ulcer induced by submucosal injection of endothelin-1 in rats

Submucosal injection of endothelin (ET) -1 induces gastric ulcer. We investigated the roles of neutrophils and adhesion molecules (intercellular adhesion molecule (ICAM)-1 and CD18) in the development of ET-1-induced ulcers in rats. UIcers were induced by submucosal injection of ET-1. Rats were injected with anti-neutrophil serum or F(ab')(2) fragments of irrelevant mouse IgG(2a) (control), anti-ICAM-1 antibody, or anti-CD18 antibody. Ulcer tissues were subjected to measurement of myeloperoxidase (MPO) activity, ulcer size, and immunohistochemical study. Within 3 hr, arterial vasoconstriction and vascular congestion were observed at sites of ET-1 injection. By 6 hr, vascular congestion had disappeared, and ICAM-1 expression had markedly increased in venules in deep portions of the mucosa and submucosa, accompanied by an increase in the number of CD18-positive neutrophils. By 48 hr. ulcers that extended into the submucosa had developed. In controls, MPO activity gradually increased and was maximal by 6 hr. Neutrophil depletion, and immunoneutralizing of ICAM-1 and CD18 inhibited the increase in MPO activity, and decreased ulcer sizes measured at 48 hr. In conclusion, ET-1 causes ischemia-reperfusion injury, and neutrophil accumulation after reperfusion mediated by the ICAM-1-CD18 pathway may be important in the development of ET-1-induced gastric ulcer.