MONITOR PEPTIDE (RAT PANCREATIC SECRETORY TRYPSIN-INHIBITOR) DIRECTLYSTIMULATES THE PROLIFERATION OF THE NONTRANSFORMED INTESTINAL EPITHELIAL-CELL LINE, IEC-6

Background/Aims: The growth-stimulating activity of monitor peptide [r at pancreatic secretory trypsin inhibitor (PSTI)-61] was evaluated in the rat intestinal epithelial cell line IEC-6. In response to food int ake, monitor peptide induces cholecystokinin release and the subsequen t secretion of pancreatic enzyme into the rat small intestine. Methods : Monitor peptide was purified from rat bile-pancreatic juice. The pro liferation of IEC-6 cells was determined by both counting cell number and [H-3]-thymidine incorporation. Ornithine decarboxylase (ODC) activ ity was assessed by radiometric technique using L-[1-C-14]-ornithine. Results: Monitor peptide(10(2)-10(5) ng/ml) induced a significant incr ease in the incorporation of [H-3]-thymidine into IEC-6 cells, and thi s effect was observed in a dose-dependent manner. A significant increa se in the cell number was also observed. An antibody specific for the synthetic NH2-terminal fragment of monitor peptide completely abrogate d the growth-stimulating effects of this peptide. In addition, monitor peptide effectively increased the ODC activity of IEC-6 cells. Conclu sions: These results indicate that monitor peptide stimulates the grow th of intestinal epithelial cells, and suggest that polyamine metaboli sm may be involved in this mechanism of growth induction.