The apical membrane of intestinal brush cells possesses a specialised, butspecies-specific, composition of glycoconjugates - on-section and in vivo lectin labelling in rats, guinea-pigs and mice

Brush cells are specialised epithelial cells that are assumed to represent chemoreceptors of the digestive tract. They comprise a small population of the epithelial cells lining the intestine, possess a unique ultrastructure and, in many aspects, resemble the receptor cells of taste buds. To charact erise glycoconjugates possibly involved in a sensory function, we investiga ted brush cells in the small intestine of three species using lectin histoc hemistry in confocal light and thin-section electron microscopy. Brush cell s of rats were selectively labelled by the sialic acid-specific lectin Maac kia amurensis agglutinin, those of guinea-pigs by the D-galactose-specific lectin Bandeiraea simplicifolia agglutinin, isolectin B-4 and those of mice by the L-fucose-specific lectin Ulex europaeus agglutinin lectin I. Lectin binding sites were consistently located in the glycocalyx of the apical me mbrane and in that of cytoplasmic vesicles. In vivo lectin Labelling reveal ed that the glycoconjugates of the apical membrane are accessible under phy siological conditions, that brush cells do not endocytose and that they pro bably possess a high membrane turnover rate. The results show that speciali sations exist in the composition of glycoconjugates forming the glycocalyx of brush cells in all species investigated. The presence of brush cell-spec ific glycoconjugates would be in accordance with the current hypothesis of a receptive function of brush cells. Differences in the specific glycosylat ion patterns among rats, guinea-pigs and mice indicate that species-specifi c adaptations exist.