The binding of the legume lectins Phaseolus vulgaris E4 and L4, Glycine max agglutinin, Vicia faba agglutinin, and Pisum sativum agglutinin to intact differentiated Caco-2 cells and to brush border membranes of differentiated Caco-2 cells was investigated, and their impact on the cellular metabolism and the microvilli of these cells was assessed. P. vulgaris isolectin E4 showed the most intense staining after binding of fluorescein isothiocyanate-labeled lectin to intact Caco-2 cells. P. sativum agglutinin showed the weakest staining intensity. The dissociation constant for P. vulgaris isolectin E4 and P. sativum agglutinin binding was 0.11 x 10(-5) and 1.69 x 10(-5) mol/L, respectively. The values of the dissociation constants for P. vulgaris isolectin L4, G. max agglutinin, and V. faba agglutinin were situated in between these extremes. Stimulation of thymidine, glucosamine, and fucose incorporation was observed after exposure to P. vulgaris isolectins and soybean agglutinin. V. faba agglutinin had an inhibitory effect, whereas P. sativum agglutinin showed little or no effect. Compared with control cells and P. vulgaris isolectin L4- and P. sativum agglutinin-incubated cells, the microvilli of P. vulgaris isolectin E4-, soybean agglutinin-, and V. faba agglutinin-incubated cells were shortened significantly. The data provide evidence that a correlation exists, not only between the dissociation constants of the lectins and the fluorescent staining intensity, but also between the dissociation constants of the lectins and the extent of the legume lectin-induced changes in the cellular metabolism.