Expression of galectin 4 in the rat small intestine during postnatal development.

We determined the expression of an endogenous lectin, galectin 4, in the rat small intestine during postnatal development. The mRNA levels of galectin 4 did not change significantly between birth and adulthood. In contrast, the protein was present at higher levels after than before weaning, and the potential ligands for galectin 4 were more highly represented in the enterocyte microvilli of weaned than of suckling rats. These results suggest possible differences either in galectin 4 mRNA stability, in its translation regulation or in the protein stability.

Expression and localization of galectin 4 in rat stomach during postnatal development.

Galectins are lectins implicated in cell-cell or cell-matrix adhesion, cell growth, the cell cycle, transcription processes, and apoptosis, and some of them are differentially regulated during pre- or post-natal development. The purpose of the present study was to determine whether the expression of galectin 4 is relevant to developmental processes during postnatal development in the rat stomach. Galectin 4 expression in the rat gastric mucosa, between birth and adulthood, was studied at the protein and mRNA levels by western and northern blotting, respectively. This lectin was localized precisely by immunoelectron microscopy. In the gastric mucosa, galectin 4 protein was present at lower levels in suckling than in weaned rats, but mRNA levels did not change significantly during postnatal development. This suggests possible differences in mRNA stability or in the translation regulation. Immunocytochemical examination of galectin 4 confirmed more highly elevated levels of the protein in endocrine, parietal, and chief cells in weaned rats than in suckling rats. Galectin 4 was more strongly localized in weaned rats than in suckling rats in the nuclei of all cell types and in or over secretory granules in endocrine and chief cells, suggesting that galectin 4 is implicated in nuclear events and perhaps in secretory processes.

Glucocorticoid-induced maturation of glycoprotein galactosylation and fucosylation processes in the rat small intestine.

We determined the role of glucocorticoids in the maturation of glycoprotein galactosylation and fucosylation processes in the rat small intestine during postnatal development. Treatment of suckling rats with hydrocortisone (HC) increased activities of an O-glycan: galactosyltransferase, and of an alpha-1,2-fucosyltransferase, through transcriptional regulation of the FTB gene. The activities of a fucosyltransferase inhibitor and of the enzymes responsible for the synthesis and degradation of GDP-fucose were unaffected by the treatment, whereas a fall in the activity of alpha-L-fucosidase was observed. These changes were accompanied by the precocious appearance of alpha-1,2-fucose residues in complex glycan chains of brush-border membrane glycoproteins that normally appear after weaning, and with a trend to increase in alpha-1,2-fucose residues in mucins. Thus, treatment of suckling rats with hydrocortisone speeds up the maturation of glycoprotein galactosylation and fucosylation processes in the small intestine. The delayed increase in glucocorticoid levels induced by prolonged nursing, or the suppression of glucocorticoids by adrenalectomy (AD) before the normal rise in the hormone, both induced a delay in the increases in activities of the O-glycan: galactosyltransferase and alpha-1,2-fucosyltransferase observed normally after glucocorticoid enhancement. Thus, glucocorticoids might play at least a partial role in the maturation of glycoprotein glycosylation observed at weaning.