Biomedical Research 16 (5) 281-286, 1995

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2 DEVELOPMENTAL EXPRESSION OE NEUROTENSIN AND GALANIN § IN THE RAT GASTROINTESTINAL TRACT 2 i

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MUNEO OKA‘, NIMA KHANDAN-—NIA2, PHILIP JoNEs2, MOHAMMAD GHATEI2 and STEPHEN ROBERT BLOOM2 ‘Department of Endocrinology, Internal Medicine, Dokkyo University School of Medicine, Mibu, Tochigi 321-02, Japan, and 2Department of Medicine, Royal Postgraduate Medical School, Hammersmith Hospital, Du Cane Road, London W12 ONN, U.K.

ABSTRACT To characterize and compare the developmental patterns of neurotensin (NT) and galanin (GAL) expression in the gastrointestinal tract, we measured both peptide content and mRNA concentrations in different regions of the rat gastrointestinal tract at different times during fetal and postnatal development. The abundance of NT mRNA in the jejunum and ileum increased from birth and peaked on day 7, subsequently decreased by day 21. In con- trast, expression of NT mRNA in the stomach and colon remained very low. Changes in NT peptide content parallelled that in NT mRNA. On the other hand, the abundance of GAL mRNA, which was expressed in all regions of the gastrointestinal tract, gradually increased until day 21 following birth. GAL peptide content increased up until day 7; thereafter, the levels of this peptide remained relatively unchanged. Thus, the gene expres- sion of NT and GAL each demonstrates a specific pattern of tissue distribution and a dif- ferent developmental pattern. These data suggest that NT and GAL gene expression and peptide content are developmentally regulated and that NT and GAL each play a different role in the gastrointestinal tract during development.

Previous studies have suggested important roles for distribution of these neuropeptides during gut several neuropeptides in maintaining the functional development should provide a better understanding and structural integrity of the gut. For example, of their roles in the gut. The purpose of this study neurotensin (NT), a gut tridecapeptide localized was to characterize and compare the developmental mainly in the distal small bowel (14, 25, 32) and pattern of NT and GAL expression in the rat gas- brain of adults (24), is an important hormone regu- trointestinal tract. To this end, we measured both lating gut motility, secretion, and mucosal growth immunoreactivity and mRNA concentrations in (1, 6, 31). Expression of such neuropeptides in the different regions of the rat gastrointestinal tract at gut is likely to be regulated during development, different times during fetal and postnatal develop- when rapid changes occur in gut structure and func- ment. tion. In fact, lower levels of NT mRNA have been found in the fetal rat ileum than in the adult (IO); MATERIALS AND METHODS similarly, fewer NT-immunoreactive cells have been found in the fetal human small bowel than in Animals the adult (28). In contrast, galanin (GAL), a 29 Eighty male Wistar rats were used in this amino acid gut peptide originally isolated from study. Twenty-one-day-old rats were kept five to porcine intestine that has been shown to be a cage and fed ad lib. Newborn animals were involved in the regulation of gut motility (3, 5, 7, kept with their mother until sacrificed. Fetal 11, 12, 26, 29), has been found to decrease after rats (—1 day) were removed immediately follow- birth in the rat stomach and duodenum (13). Thus, ing the death of their mother and decapitated elucidation of any changes in the expression and instantly.