Radioautographic Visualization of the Deposition of a Phosphoprotein at the Mineralization Front in the Dentin of the Rat Incisor

A peptide that is rich in organically bound phosphorus and contains abundant serine residues has been identified in the dentin of man (1), fetal bovine (2, 3), and rat (4). This phosphoprotein may play a role in mineralization (5-9). Butler et al. (4) reported that the phosphoprotein of rat incisor dentin constituted 10.8 % of the proteinaceous material recovered from decalcified incisor teeth while collagen comprised 84%. Since the phosphorus content of the phosphoprotein was estimated at 3.29 % and that of collagen at 0.19% (4), much of the phosphorus taken up in organic form by the incisor would likely be present as phosphoprotein. With this in mind, it was decided to inject [~3P]phosphate into rats and examine the