Ultrastructural visualization of concanavalin A binding sites using alkaline phosphatase-labeled Con A and ultrathin glycol methacrylate sections.

A method for the visualization of concanavalin A (Con A) binding sites by electron microscopy of glycol methacrylate sections is presented. This method, which is an application of the alkaline phosphatase-labeled Con A conjugate technique, solves the problems not only of limited penetration of chemicals into tissue blocks but also of injuries to tissue sections due to irritative reagents experienced in Con A-peroxidase staining. Glycol methacrylate sections are incubated successively with an alkaline phosphatase-labeled Con A solution and a lead citrate medium for the enzyme activity. Different kinds of tissues from adult rats have been used to test the method; tracheal cartilage, aorta and jejunum. The localization of Con A binding sites demonstrated by this method is consistent with the results of other published studies. Appropriate controls have been performed (ie., omission of the conjugated lectin, lectin plus its inhibitor) and these substantiate the specificity of the method.