Penetration and uptake of colloidal gold-labeled concanavalin A in the junctional epithelium of the rat.

A complex of colloidal gold and concanavalin A (CG-Con A) with various biological properties and high ultrastructural resolution was applied into the sulcus of rat molar gingiva and traced with an electron microscope for three hours to examine the cytological changes occurring in the cells of the junctional epithelium (JE) during penetration of extrinsic irritants, and to determine the roles of JE cells in such a circumstance. While the penetration of CG-Con A was impeded on the surface of keratinized oral gingival/sulcular epithelium, CG-Con A penetrated swiftly through JE into the connective tissue. In the process of penetration, CG-Con A was taken up by lysosomal and vacuolar structures of JE cells in which degenerative changes were often provoked. Degeneration of JE cells was seen selectively in the second and/or third cell layers from the innermost cell layer of JE. It was assumed that JE cells by their phagocytic activity might participate in the first line of defense against extrinsic irritants. On the other hand, the phagocytic activity of JE cells seems also to be involved in tissue destruction, if the amount and/or toxicity of irritants exceed the dissimilating capacity of JE cells.