Ileal proglucagon gene expression in the rat: characterization in intestinal adaptation using in situ hybridization

Proglucagon-derived peptides are potential mediators of the adaptive response of the terminal ileum to massive small bowel resection. Ileal proglucagon messenger RNA (mRNA) levels increase during ileal adaptation. The present study explored the cellular basis of this response.

Sections of control ileum, ileum 4 days after resection, and pancreas were analyzed by in situ hybridization with 35S-labeled complementary RNA (cRNA) probes.

Both the proglucagon and the peptide YY cRNA probes hybridized to discrete cells in the ileal mucosa, the disposition of which corresponds to that reported for intestinal L cells. Four days after resection there was a marked increase in the intensity of the signal for both probes without an increase in cell number. Insulin and histone H3 probes were used as controls to confirm the specificity of the hybridization seen with the L-cell specific, proglucagon, and peptide YY probes.

The increase in proglucagon mRNA levels after massive small bowel resection is caused by an increase in the cellular content. The parallel increase in PYY mRNA levels implies an L cell--rather than a proglucagon gene--specific response.