Glucagon-like immunoreactive peptides in a rat ileal epithelial cell line (IEC-18)

The presence of cells containing glucagon-like immunoreactive (GLI) peptides was demonstrated in a rat ileal epithelial cell line (IEC-18) by both immunofluorescence and radioimmunoassay. When cell extracts were subjected to gel filtration chromatography, the cells were found to contain 3.5 Kd glucagon in addition to significant quantities of large molecular weight GLI peptides (apparent molecular weights of 4, 6, 8 and 10 Kd) and a 9 Kd peptide with apparent glucagon immunoreactivity. This was in contrast to extracts of adult rat ileum, which contained only large molecular weight GLI peptides (apparent molecular weights of 6 and 12 Kd). Production of GLI peptides by the IEC-18 cells was stimulated by glucose (p less than 0.02) and inhibited by insulin (p less than 0.01). In conclusion, these results demonstrate that the IEC-18 cells produce both GLI peptides and glucagon, and thus support the notion that proglucagon processing is cell-specific. IEC-18 cells may therefore provide a tool for investigations of some aspects of GLI peptide and glucagon synthesis.