Monitor peptide (rat pancreatic secretory trypsin inhibitor) directly stimulates the proliferation of the nontransformed intestinal epithelial cell line, IEC-6.

BACKGROUND/AIMS: The growth-stimulating activity of monitor peptide [rat pancreatic secretory trypsin inhibitor (PSTI)-61] was evaluated in the rat intestinal epithelial cell line IEC-6. In response to food intake, monitor peptide induces cholecystokinin release and the subsequent secretion of pancreatic enzyme into the rat small intestine.

METHODS

Monitor peptide was purified from rat bile-pancreatic juice. The proliferation of IEC-6 cells was determined by both counting cell number and [3H]-thymidine incorporation. Ornithine decarboxylase (ODC) activity was assessed by radiometric technique using L-[1-14C]-ornithine.

RESULTS

Monitor peptide (10(2)-10(5) ng/ml) induced a significant increase in the incorporation of [3H]-thymidine into IEC-6 cells, and this effect was observed in a dose-dependent manner. A significant increase in the cell number was also observed. An antibody specific for the synthetic NH2-terminal fragment of monitor peptide completely abrogated the growth-stimulating effects of this peptide. In addition, monitor peptide effectively increased the ODC activity of IEC-6 cells.

CONCLUSIONS

These results indicate that monitor peptide stimulates the growth of intestinal epithelial cells, and suggest that polyamine metabolism may be involved in this mechanism of growth induction.