Distribution of 35S-sulfate within the transseptal ligament of the mouse

The distribution of 35S-sulfate-labeled macromolecules was examined within three regions of the transseptal ligament: the 1) mesial, 2) middle and 3) distal thirds. Swiss mice, 6 weeks of age, were injected with 35S-sulfate and killed after 1, 6, and 12 hours and 1, 2, 3, 4, 5, and 7 days. Silver grains and cell nuclei were counted on autoradiographs which had been counterstained by the Van Gieson method, and mean counts were analyzed statistically. Analysis of variance revealed no significant differences in mean number of cell nuclei between regions throughout the course of the experiment. 35S-sulfate was rapidly incorporated into the transseptal ligament macromolecules. Grain counts were highest 6 hours after injections: counts were highest over the middle and lowest over the mesial thirds of the ligament. The rate of grain removal was significantly higher in the middle third compared to the mesial or distal thirds (P less than 0.001) and was significantly lower in the mesial third compared to the middle or distal thirds (P less than 0.001). The half-life of labeled macromolecules was significantly greater in the mesial and distal thirds than in the middle third (P less than 0.005). The data demonstrate significantly higher rates of turnover of 35S-sulfate-labeled macromolecules in the middle region of the transseptal ligament. Since cellular density was similar throughout the transseptal ligament, higher turnover rates of 35S-sulfate-labeled macromolecules probably indicate higher rates of cellular activity in this region, possibly a result of tissue remodeling coincident to stresses generated by occlusal forces and physiologic drift of the adjacent teeth.