| Abstract: | The profile of cyclooxygenase and lipoxygenase products in normal rat colonic epithelium and subepithelium was examined. Colons were thoroughly perfused to eliminate contamination with blood. Two preparations of colonic epithelium were employed. The first consisted of intact colonic crypts and epithelial sheets. The second yielded single cell suspensions of superficial versus proliferative epithelial cells. Lipoxygenase product formation by colonic epithelium as measured by hydroxyeicosatetraenoic acid (HETE) and leukotriene B4 (LTB4) production (5-HETE greater than 12-HETE greater than 15-HETE greater than LTB4) accounted for 58% of the total colonic production of these moieties, whereas epithelium accounted for only 20% of total colonic protein. By contrast, prostaglandin (PG) E2 and PGF2 alpha production occurred predominantly (greater than 97%) in the subepithelial layers. The present studies also demonstrate markedly higher levels of accumulation of lipoxygenase products in proliferative versus superficial epithelial cells, whereas prostaglandin accumulation was greater in superficial cells. Previous studies have supported a role for lipoxygenase and cyclooxygenase products in the control of colonic secretion, inflammatory cell infiltration and proliferative activity. The present results raise the possibility that the striking differences in the sites of production of these products within the colon has functional implications. |
