Differential localization of calmodulin, the 67kDa calcimedin and calpactin II in secretory ameloblasts.

By using specific antibodies, we have shown by Western blots that dental tissues contain calmodulin, the 67 kDa calcimedin and calpactin II. Moreover, by immunogold electron microscopy, we were able to compare the intracellular distribution of these three calcium-binding proteins in secretory ameloblasts. They were all found in the cytosol of these cells but only calcimedin was detected in the mitochondria. Calpactin II was the only one present in secretory vesicles. Twice as much calmodulin and calpactin II were detected in cell bodies as in Tomes' processes, but calcimedin was more abundant in the latter. The presence of these calcium mediators in well defined areas of ameloblasts may indicate differential ways for these cells to regulate different calcium-dependent processes during enamel formation.