The Protein Matrixes of the Teeth and Periodontium in Hamsters: A Tritiated Proline Study

¹ Howard University College of Dentistry, Washington, D.C.

This investigation has presented observations regarding (1) scintillation counting of tritium activity in the plasma of hamsters given ³H-proline, (2) light microscopic autoradiographic observations of the protein matrixes of the teeth and periodontium, and (3) the relationship between the plasma tritium level and autoradiographic observations.

Tritium activity in the plasma was detected as early as 2.5 minutes postinjection. The autoradiographs clearly showed intracytoplasic labeling of the ameloblast, odontoblast, and osteoblast cells 15 minutes postinjection. The plasma tritium curve showed two peaks, one at 10 to 15 minutes and a second at 4.5 to 6.5 hours postinjection. The second peak appeared to parallel rather closely the time when the autoradiographs showed the tracer being initially transferred from an intracellular to an extracellular location by most of the cellular elements. Tritium activity in the plasma extended over a period of approximately 20 days. The autoradiographs suggested that the plasma activity beyond 5 days postinjection was in a form nonutilizable by the cells.

Between 15 minutes and 4 hours, the autoradiographs showed (a) the passing of the tracer from an intracellular to an extracellular location with evidence of preferential intracytoplasmic localization of the tracer over the region corresponding to the Golgi apparatus by the ameloblast and odontoblast cells at 1 hour postinjection. (b) A comparison of the ameloblast and odontoblast cells along the dentinoenamel membrane (pre-enamel matrix formation) showed the odontoblasts to be more heavily labeled; whereas, along the dentinoenamel junction (post-enamel matrix formation), the ameloblasts were more heavily labeled.

The 24-hour autoradiographs showed a conspicuously more diffuse distribution of labeling over the enamel matrix compared with dentin matrix.

The 59-day autoradiographs showed a distinct decrease in the amount of labeling of the fibers of the periodontal membrane, pulp, and alveolar bone and essentially no change in the amount of tracer over the dentin and cementum.

The results of this investigation indicate a distinct difference in the renewal rate of the collagenous structures of the periodontal ligament, pulp, and alveolar bone compared with that of the collagenous matrixes of dentin and cementum.