Characterization of rat colonic cell surface glycoconjugates by fluoresceinated lectins. I. Importance of fixation techniques.

Cryostat and paraffin embedded sections from cecum, proximal and distal colonic segments of male Sherman rats were examined by fluorescence microscopy after labeling with six fluorescein-conjugated lectins. These FITC-conjugated lectins were used as specific probes to define the labeling pattern of carbohydrate containing components of the lumenal and basolateral surfaces of epithelial cells, goblet cell mucin and lumenal mucin at all three sites. Marked regional differences in labeling were detected, indicating that the various carbohydrate components of these cells differ significantly along the length of the colon. Furthermore, the patterns of labeling components with each lectin appeared to vary depending on the fixation technique employed. Cryostat preparations generally resulted in a broader distribution of label and more intense staining with these lectins than fixed paraffin sections. While the reason(s) for these variations remain unclear at this time and will require further studies, the present data emphasize the importance of the fixation method when interpreting results obtained utilizing FITC-conjugated lectins.