Brush Cells of the Mouse Intestine Possess a Specialized Glycocalyx as Revealed by Quantitative Lectin Histochemistry: Further Evidence for a Sensory Function

Abstract

Brush cells occur in the epithelium of the small intestine and in various other epithelia of endodermal origin. Ultrastructural and histochemical characteristics suggest that they represent sensory cells. Because the apical membrane of brush cells might be involved in and specialized for (chemo-)receptive functions, we investigated the composition of the glycocalyx and compared it with that of enterocytes. Ultrathin sections of murine small intestine were labeled with a panel of eight lectins. Their binding sites in the brush border and on vesicles of the apical cytoplasm were detected by colloidal gold and quantified using image analysis. The glycocalyx of brush cells contained significantly higher amounts of L-fucose residues than that of enterocytes, as detected by the lectins UEA-I and LTA. In contrast, most of the other lectins bound more avidly to the glycocalyx of enterocytes. The cytoplasmic vesicles closely resembled the apical membrane in their labeling pattern. Quantitation of the brush cells' distribution revealed that the epithelia of the Peyer's patches contained 10-fold higher numbers of brush cells than the small intestinal mucosa distant from lymphoid tissue. We conclude that brush cells possess a glycocalyx with a specialized composition and differ significantly from enterocytes. Because similar peculiarities of the apical membrane have previously been described for sensory cells of the olfactory and gustatory organs, this study provides further evidence in favor of a sensory function of brush cells.