GLYCOCONJUGATES OF THE NORMAL HUMAN COLORECTUM - A LECTIN HISTOCHEMICAL-STUDY

Previous studies of the normal human colorectum by lectin histochemist ry have used a mixture of tissues, including those derived from colons harbouring neoplasia and inflammatory bowel diseases. In the current investigation, tissues from patients without either of these condition s have been examined with a wide panel of lectins, encompassing specif icities directed against both N- and O-linked sequences, using an avid in peroxidase revealing system and evaluated with a semiquantitative s coring method. The results of binding of these lectins have been compa red with those seen in the resection margins of (at least 5 cm away fr om) colorectal carcinomas. Consistent regional variations were noted b etween right- and left-sided colonic tissues, with more diverse glycan structures and a greater sialyl content in the distal colon. There wa s evidence of graduation of formation of oligosaccharide chains in dev eloping crypts, possibly related to the maturation and expression of g lycosyl transferases responsible for the incorporation of mannose resi dues of N-linked oligosaccharides and of N-acetylgalactosamine and N-a cetylglucosamine. Comparison with previous reports has revealed some v ariations, possibly related to tissue fixation and processing and to l ectin concentrations employed, which raises the question of standardiz ation of methodologies in lectin histochemical investigations.