Gastrin and epidermal growth factor induction of ornithine decarboxylase in rat colonic explants

An organ culture system was utilized to examine the effect of gastrin (G-17-I) and epidermal growth factor (EGF) on colonic mucosal ornithine decarboxylase (ODC) activity, and the expression of the ODC gene. Exposure of colonic mucosal explants to either gastrin or EGF (50-500 ng/ml) for only 4 h resulted in a profound stimulation (150-600%) in ODC activity over the basal level. These increases were essentially abolished by difluoromethylornithine (DFMO; 2 nmol/ml) or CaCl2 (2 umol/ml). Gastrin also activated the ODC gene in the colonic mucosa as evidenced by increased steady-state ODC mRNA levels in the colonic mucosal explants after 4 h exposure to the hormone, when compared with the controls. It is concluded that colonic mucosal ODC is responsive to both gastrin and EGF.