Polyamine participation in the maturation of glycoprotein fucosylation, but not sialylation, in rat small intestine.

The aim of this study was to determine the role of polyamines in the diet-related maturation of the intestinal glycoprotein glycosylation during postnatal development in the rat. The activity of alpha-2,6-sialyltransferase and the sialylated forms of glycoproteins in the intestinal brush-border membranes were found to decrease considerably after weaning, in parallel with the intestinal level of putrescine. By contrast, the activity of alpha-1,2-fucosyltransferases, the mRNA levels for two alpha-1,2-fucosyltransferase genes, FTA and FTB, and the fucosylated forms of glycoproteins all increased after weaning, in parallel with the levels of spermidine and spermine. These results suggest a possible role of polyamines in the evolution of glycosylation. The treatment of suckling rats with spermidine or spermine reproduced the high intestinal levels of these polyamines corresponding to those normally found after weaning. After these treatments, a rise in the activity of the alpha-1,2-fucosyltransferase was observed, associated with a fall in alpha-L-fucosidase activity. The alpha-1,2-fucosyltransferase FTB gene was found to be regulated at the transcriptional level, but not by its inhibitor, fuctinin. The result of these variations was the precocious appearance of several alpha-1,2-fucoproteins, which are normally found in brush-border membranes after weaning. The treatment of suckling rats with putrescine, which induced only a transitory rise in intestinal putrescine, had a similar but weaker effect on the fucosylation process than spermidine or spermine, and treatment with ornithine was ineffective. alpha-2,6-Sialylation was not affected by any of the treatments. Spermidine and spermine turned out to be more effective than putrescine for intestinal glycoprotein fucosylation, but did not affect their sialylation. Spermidine and spermine, whose intestinal levels where found to increase at weaning time, may have been partly responsible for the natural evolution of the intestinal glycoprotein fucosylation that occurred during this period.