The binding of calcium within the Golgi saccules of the rat odontoblast

Odontoblasts of developing rat molar teeth were treated with OsO4-pyroantimonate to ascertain the localization of calcium. In addition, some tooth germs were incubated in solutions which were intended to allow for the escape of diffusible ions prior to fixation in OsO4-pyroantimonate. In tissues treated directly with OsO4-pyroantimonate, antimonate reaction product was found chiefly in abacus bodies and secretory granules of the Golgi region and in secretory granules in the distal pole of the cell. Lesser amounts of reaction product were found in the extracellular space, mitochondria, nucleus and generally throughout the cell. Tissues pre treated to allow for the escape of diffusible ions showed reaction product, identified as containing calcium, only in the abacus bodies and secretory granules. These results are considered to reflect the binding of calcium within the Golgi apparatus of the odontoblast. Moreover, since it has been shown by others that the abacus bodies and secretory granules contain collagen precursor, it is suggested that the collagen precursor is being seeded with calcium within the Golgi apparatus and that this intracellular calcium binding will play a role in facilitating the major wave of extracellular mineralization of the dentin which is to follow.