Abstracts
1997 Digestive Disease Week

Neurotensin gene expression is not affected by gut transposition.

X-M Wang, RP Thomas, BM Evers. Department of Surgery, University of Texas Medical Branch, Galveston, TX.

Neurotensin (NT), an important regulatory hormone of the gut that stimulates gut mucosal growth, is released by intraluminal fat. Expression of the NT gene (designated NT/N) is developmentally regulated in the adult small bowel with maximal expression noted in the distal ileum; the mechanisms responsible for this strict spatialspecific expression pattern are not known. The purpose of this study was to determine whether the NT/N expression is altered by transposing the distal gut to a more proximal location. METHODS. Male Fischer 344 rats underwent operation and either transposition of a 5-8 cm segment of distal ileum into the proximal jejunum or sham operation (bowel division and reanastomosis). Rats were maintained on regular chow and killed two months after operation; the transposed and sham-operated segments of gut were removed and a portion processed for histology. The remainder of the tissue was extracted for total RNA and analyzed by both RNase protection and Northern blot using a specific rat NT/N probe. For comparison, expression of another distal gut peptide, peptide YY (PYY), was also determined. RESULTS. At the end of two months, the transposed ileum appeared morphologically similar to the native jejunum. In contrast, there was no difference in NT/N gene expression in the transposed ileum compared with both the sham segments and normal (nonoperated) ileum by either RNase protection (Fig. 1 [figure not available]) or Northern blot. Moreover, expression of PYY was unchanged in the transposed gut (Fig. 2 [figure not available]). CONCLUSIONS. We have found that transposition of the distal ileum to a more proximal location produced a marked change in morphologic appearance; however, expression of the gut hormones NT/N and PYY remain unaltered. Thus, the strict spatial-specific pattern of gut hormone gene expression appears to be "imprinted" and is maintained regardless of location along the longitudinal gut axis. These findings are important to our understanding of the mechanisms controlling expression of these regulatory hormones.