Activity of alkaline and acid phosphatases in dental epithelial cells and enameloid during odontogenesis in two teleost fish, Oreochromis niloticus and Tilapia buttikoferi

The dental epithelial cells and enameloid at the stages of enameloid matrix formation, mineralization and maturation in the teleosts Oreochromis niloticus and Tilapia buttikoferi were investigated by means of enzyme histochemistry in order to identify their functions associated with the structural modification. No marked enzyme activities were found in the inner dental epithelial cells in the stage of enameloid matrix formation, although the outer dental epithelial cells often exhibited moderate alkaline phosphatase (ALPase) activity. In the stages of enameloid mineralization and maturation, the inner dental epithelial cells, which possessed a ruffled border at the distal ends, showed intense ALPase activity at their lateral and proximal cell membranes. At the same time, many acid phosphatase (ACPase)-positive vesicles and granules were localized at the distal cytoplasm of the inner dental epithelial cells. The outer dental epithelial cells, which contained well-developed labyrinthine canalicular spaces, showed neither marked ALPase nor ACPase activity. It is postulated that the dental epithelial cells in these two teleosts are mainly involved in the removal of the organic matrix from the enameloid, and in material transport to the enameloid during the later half of odontogenesis.