QUANTITATIVE HISTOCHEMISTRY OF THE DEVELOPING HAMSTER TOOTH: ALKALINE PHOSPHATASE AND LACTIC DEHYDROGENASE

1. It has been possible to adapt the quantitative histochemical technique of microdissection and microchemical assay for the study of the quantitative distribution of alkaline phosphatase and lactic dehydrogenase activity in the first maxillary molar of the hamster, between birth and 4 days of age. 2. The zones of the tooth buds dissected out and assayed were: stellate reticulum, stratum intermedium, ameloblasts, dentine plus enamel, odontoblasts, three areas of the dental papilla, and the cervical loop. 3. The quantitative results for the alkaline phosphatase distribution were found to agree qualitatively with the results obtained by the Gomori and azo dye staining techniques, except that the staining techniques gave falsely negative reactions at low activities. 4. Alkaline phosphatase activity was lowest in the zones furthest from dentine and enamel formation, while the two zones of cells most intimately concerned in the formation of dentine and enamel did not show the highest activity; in fact the ameloblast zone was one of the lowest in activity. The highest zones of activity, stratum intermedium and sub-odontoblastic papilla, were immediately next to the cells forming the matrices of dentine and enamel. 5. These facts are considered to be supporting evidence for the theory of Neuman and Neuman regarding the "detoxifying" properties of alkaline phosphatase in a "barrier" surrounding the sites of calcification. 6. The levels of lactic dehydrogenase activity were of the same order of magnitude in all the cellular zones. The zones furthest removed from enamel and dentine formation occupied the lower part of the range found.