Autoradiographic Analysis of Labeling Indices and Migration Rates of Cellular Component of Mouse Incisors Using Tritiated Thymidine (H³TDR)

¹ Medical Research Center, Brookhaven National Laboratory, Upton, Long Island, New York

The proliferative potential of the cellular component of mouse incisors and the migration rate of ameloblasts were studied autoradiographically in 5-week-old female mice with tritiated thymidine. Preameloblastic and preodontoblastic populations exhibited the highest labeling indices of 0.292 and 0.290, respectively. One hour after the tritiated compound administration, no labeled ameloblasts and odontoblasts were observed. Labeling indices of pulp cells and fibroblasts in the periodontal membrane were small. The migration rate of ameloblastic cells was measured from 1 hour to 24 days and was found to be linear with time beyond 15 hours. Twenty-four hours appeared to be required for completing proliferation and maturation of ameloblasts and to reach the functional zone. The average migration rate of ameloblasts was 365 µ per day during the observation period of 24 days. Nine days after maturation, labeled ameloblasts showed signs of degeneration by the appearance of globular structures in the stratum intermedium and ameloblastic layer. The average daily eruption rate of the incisor was measured grossly (338 µ) and was found to correlate with the migration rate of ameloblasts assessed microscopically (365 µ).

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