The growing interest in glycoconjugates
expressed and released by the epithelium of the intestinal
mucosa is tightly related to the multiple functional roles
attributed to sialic acid and its derivatives. In the present
work, biotin and HRP conjugated lectins were used to
detect the sialylation pattern and to identify specific
structural features of sialoderivatives in the rat colon. In
particular, the occurrence and distribution of sialic acids
linked a2,6 to D-Gal/D-GalNAc and a2,3 to D-Gal were
directly demonstrated with SNA and MAL II binding,
respectively. In addition, in order to by-pass the
specificity problems of SNA and MAL II as
histochemical reagents, as well as to look for additional
and complementary information about acetylation
degree and sites, we combined sialidase digestion,
potassium hydroxide deacetylation, and differential
periodate oxidation with PNA and DBA binding. The
data showed the distribution and structure of sialic acidß-
D-Gal(1-3)-D-GalNAc and sialic acid-D-GalNac
sequences, which proved to be widely distributed as
cellular components or secretory products in surface
goblet cells and crypt cells of the colonic epithelium. A high degree of O-acetylation, with acetyl groups mainly
at 9 and 4 positions, was found, showing an increasing
gradient from the proximal to distal portion of the colon.
These results, which largely reproduce the sialylation
pattern in other species, contribute new insights in
defining the tissue specific expression of sialoderivatives
in the colonic mucosa, and testify to their high
heterogeneity which the wide range of sialic acid
functional correlates in the intestinal tract depend on
