Journal
TOXICOLOGIC PATHOLOGY
Volume 33, Issue 2, Pages 239-245Publisher
SAGE PUBLICATIONS INC
DOI: 10.1080/01926230590906512
Keywords
rat; COX-1; COX-2; immunohistochemistry; NSAID; intestine; ileocaecal junction
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The aim of this study was to use immunohistochemistry with morphometry to investigate COX-1 and COX-2 expression in the normal rat gastrointestinal (GI) tract and examine if sites of ulceration previously observed with long-term COX-2 inhibitor administration in mice correlate with differential COX- I /COX-2 expression. COX-2 positive cells were observed predominantly in the apical lamina propria of intestinal villi with fewer cells in the mucosal epithelium. The highest level of COX-2 expression was observed at the ileocaecal junction (ICJ). COX-2 expression was also present in parasympathetic ganglia of the submucosa and inuscularis. In the stomach, the highest grade of COX-2 expression was observed in the apical lamina propria of the fundus adjacent to the junctional ridge. In contrast, COX- I positive cells within the lamina propria were evenly distributed along the GI tract but were present in higher numbers than COX-2 positive cells. The mean level of COX- I expression at the ICJ was not significantly different from the ileum and caecum. Evidence that the highest level of COX-2 expression in normal rats is located on the ileal side of the ICJ provides the first mechanism to explain spontaneous ulceration and perforation of the distal ileum in COX-2-/- animals.
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