Characterization and immunocytochemical localization of dentine phosphoprotein in rat and bovine teeth

Dentine phosphoprotein (DPP) was isolated from unerupted bovine molars and from rat incisors. The proteins were characterized biochemically and used to immunize rabbits and guinea pigs. Antibody activity was investigated by enzyme-linked immunosorbent assay (ELISA). Guinea-pig anti-rat DPP did not cross-react with bovine DPP, but rabbit anti-bovine DPP did cross-react with rat DPP. Anti-rat DPP antiserum was applied to cryotome sections of rat molar tooth germs and DPP immunoreactivity was seen in dentine, odontoblasts, odontoblast processes and pre-ameloblasts. Anti-bovine DPP antiserum reacted positively in bovine dentine and dentinal tubules. When this antiserum was applied to rat tissue, predentine was positive but dentine was negative. Adsorption experiments with DPP, purified by methods including and excluding precipitation with calcium, suggested that non-calcium precipitable DPP is present in rat predentine. Rat and bovine DPP are thus species-specific and DPP is synthesized by the odontoblasts, transported through their processes and secreted into the dentine.