LAMININ AND COLLAGEN-IV DISTRIBUTION AND ULTRASTRUCTURE OF THE BASEMENT-MEMBRANE OF THE GINGIVA OF THE RAT INCISOR

The continuous growth of the rat incisor is associated with renovation of the junctional epithelium and resorption of the periodontal ligame nt. The circumdental papilla separates the connective tissue suffering resorption from the rest of the gingiva. Laminin and collagen IV were detected by the immunoperoxidase technique on the basement membrane o f all regions of the gingival epithelium of the rat incisor, except th e internal basal lamina and the internal surface of the circumdental p apilla. The internal basal lamina is formed by a granular electron-den se material, without the organization of a typical basal lamina. Areas of the internal surface of the circumdental papilla, negative for lam inin and collagen IV, lack the basal lamina. These data suggest that t hese molecules are not components of the dento-epithelial junction of the distal surface of the rat incisor. In addition, the basal lamina i s absent or fragmented on the internal surface of the circumdental pap illa, adjacent to the areas of the connective tissue undergoing resorp tion.