Biochemical study of changes in non-specific alkaline phosphomonoesterase activity during mouse tooth ontogeny

Abstract

The reaction velocity of an alkaline phosphatase substrate (paranitrophenylphosphate) was measured during tooth ontogeny to help clarify the biological function of alkaline phosphatase (APase, EC 1.3.1.3). Mouse molars from the early bell stage to adult mature stages were used. Epithelial and mesenchymal components of tooth germs were analyzed separately, and crowns only from fully developed teeth. After homogenizing in Triton X-100 detergent, the rate of hydrolysis of paranitrophenylphosphate was then determined. Low enzyme activities and statistically non-significant differences were seen in the epithelial and mesenchymal parts of tooth germs. One day after birth, a significant increase was seen in both parts, but activity was 4 times higher in the mesenchymal part, continuing up to the 7th day. At day 11, a decrease occurred in both parts. Adult levels were reached by day 18. The protein content of the epithelial part began to rise before the increase in APase activity occurred. It is probable that the reactions catalyzed by APase are activated in the germs between the 18th prenatal and first postnatal days. The onset of the rise in enzyme activity in the 2 components corresponds with the onset of the secretory phases.