Swainsonine toxicosis mimics lectin histochemistry of mannosidosis

Cells affected by locoweed (Astragalus lentiginosus) and Swainsona galegifolia toxicosis or mannosidosis exhibit similarities in their catabolism of N-linked glycoproteins and accumulation of cytoplasmic vacuoles. We used nine different biotinylated lectins as histochemical markers for specific sugars and avidin-biotin-peroxidase complex as a visualant to study the cells affected with these conditions. Since locoweed and Swainsona spp block mannosidase activity, we expected a similar lectin staining pattern in cells under these conditions as that seen in mannosidosis. Concanavalia ensiformis agglutinin, wheat germ agglutinin and succinyl wheat germ agglutinin stained the undegraded glycoproteins and oligosaccharides stored in the lysosomes of affected cells in all three conditions. Bandeirea simplicifolia-I, Dolichos biflorus agglutinin, peanut agglutinin, Ricinus communis agglutinin-I, soybean agglutinin and Ulex europaeus agglutinin-I did not stain any of these cells. These results indicate that in all three conditions there is an accumulation of undegraded oligosaccharides that contain alpha-mannosyl and beta-N-acetyl glucosamine residues which are revealed by lectin staining in the vacuoles of all affected cells.