Concanavalin A binding sites of rough endoplasmic reticulum containing intracisternal microtubules in canine neurones

Lectin histochemistry was used to identify sugar residues of IM-containing RER in elderly canine sympathetic ganglionic neurones. IM-inclusions stained with ConA-peroxidase conjugate, but not with soybean agglutinin (SBA), wheat germ agglutinin (WGA), peanut agglutinin (PNA), Dolichos biflorus agglutinin (DBA), Ricinus communis agglutinin (RCA I) and Ulex europaeus agglutinin (UEA I). ConA-binding sites were visualized within cisternae of RER containing IM; reaction product was localized in IM-containing RER cisternae and IM. Inhibition with specific sugars (0.1 M alpha-methyl-D-mannoside or 0.5 M D-glucose) blocked the binding of ConA to IM-inclusions and normal Nissl substance. When a low sugar concentration (5 x 10(-3) M alpha-methyl-D-mannoside or 0.2 M D-glucose) was employed, IM-inclusions were still strongly ConA-positive, but normal Nissl substance was not. These results demonstrate that IM-containing RER have an excessive amount of carbohydrates (mannose or glucose-rich sugars) which are essentially detected in flattened RER under normal conditions and further indicate that glycoproteins in IM differ from those in cytoplasmic microtubules.