A western-blotting study of enamel glycoproteins in rat experimental fluorosis.

Experimental fluorosis was induced in order to get information on enamel protein glycosylation, using Western-blotting methodology with peroxidase-labelled concanavalin A. Fluoride inhibited amelogenin degradation, especially the production of intermediate forms. Within the non-amelogenin family of proteins there were changes in both the conventionally stainable components and the glycoconjugates revealed by lectin only. Fluoride influenced the whole extracellular processing of enamel proteins including movement between the mineral and non-mineral compartments. A different degradation scheme of enamel proteins, which also affects the glycoconjugates, might be of importance in the properties of the fluorosed enamel surface and its interactions with the oral environment.

Enamel proteins within two preferentially used animal models.

Two different models have been used to study enamel proteins: rodent incisors and bovine or porcine tooth germs. In the present experiment proteins were sequentially extracted from forming enamel of rat incisors and bovine tooth germs and examined using SDS-PAGE. The Coomassie-blue staining of amelogenins from both species revealed very similar patterns, which indicates a rather common processing, although developed at different rates. Non-amelogenin proteins behave differently when Concanavalin-A probing was used. Bovine non-amelogenins contain amido-black stainable proteins which are not recognized by lectin, contrary to rat enamel. If those proteins are albumin or albumin derived, as recently suggested, the observed discrepancy might be explained by the non enzymatic glycation known to occur on circulating albumin. In that case it would be a consequence of the use of adult rats in which circulating albumin is partly glycated versus bovine foetuses in which albumin would not be significantly glycated. Finally both species contain glycoproteins within non-amelogenins, which remain to be more precisely defined.

Proteins of the mineral compartment of bovine fetal enamel share common antigenic determinants with serum proteins.

Two fractions were separated from the proteins of the mineral compartment of bovine developing enamel on the basis of their affinity for the lectin concanavalin-A. A monoclonal antibody was prepared by the hybridoma technique against the Con-A-binding fraction. This antibody and a commercial polyclonal antibody against bovine serum albumin were used to examine the relationship between those proteins, serum albumin and alpha-2HS glycoprotein, two proteins concentrated within dentin and bone matrices. The Con-A-unbound fraction reacted with the anti-albumin antibody and the antibody against the Con-A-binding fraction recognized the alpha-2HS glycoprotein. These data fully support the presence of significant levels of proteins related to serum components in the mineral compartment of developing enamel matrix.