Effect of epidermal growth factor on polyamine-synthesizing enzymes in rat enterocytes

A number of peptides having trophic activity on gastrointestinal mucosa and growth factors are known to induce small intestinal ornithine decarboxylase (ODC) activity. The effect of peptides on ODC and S-adenosylmethionine (SAMDC) activities (key enzymes in polyamine biosynthesis) in isolated enterocytes is unknown. Male Sprague-Dawley rats were fasted for 72 h and injected intraperitoneally with epidermal growth factor (EGF), pentagastrin, or glucagon, or intragastrically with EGF. A similar volume of water served as a control. Villus tip, midvillus, and crypt cell fractions were collected and identified. ODC and SAMDC activities were determined in these cells 4 h after peptide injection. EGF given intraperitoneally, but not intragastrically, stimulated ODC activity along the cryptvillus column. Pentagastrin and glucagon did not induce polyamine biosynthetic enzyme activity. ODC and SAMDC activities in intestinal mucosal scrapings from fasted animals also were increased 2-4 h after intraperitoneal EGF treatment. It is possible that EGF binding at the serosal surface of the crypt enterocyte and subsequent ODC induction is important in initiating the cellular proliferation that is known to occur after treatment with this peptide.