Phosphohydrolase activities in developing and mature dental tissues.

In the course of the odontogenesis of bovine incisors several clearly distinguishable phosphohydrolase activities are observed in the pulp and in dental hard tissues. Using various substrates and inhibitors, unspecific alkaline phosphatase, two isoenzymes of acid phosphatase, Ca2(+)-activated ATPase and inorganic pyrophosphatase are characterized. The enzymatic activity of alkaline phosphatase in pulp and hard tissues is significantly high at the beginning of dentine and enamel mineralization. The specific activity of this enzyme decreases quite fast with the beginning of root formation, then more slowly, until it reaches a constant final value. Histochemical studies show that during mineralization the maximum of alkaline phosphatase activity is in the subodontoblasts. Lower enzyme concentrations are found in the stratum intermedium and in the outer enamel epithelium during that process. The specific activities of ATPase, acid phosphatases and pyrophosphatase show little temporal variation during tooth development, but they also appear in a characteristic spatial pattern in the dental tissues.