The effects of ATP depletion and ionophore A23187 on calcium transport in the secretory rat enamel organ.

An in-vitro system was used to study the effects of ATP depletion in the cells of the enamel organ and the use of the calcium ionophore A23187 on the mineralization of rat molar secretory stage enamel and 45Ca-movement through the enamel organ. Mineralization of the explants and 45Ca-uptake by the enamel were both enhanced by ATP depletion. No changes in these parameters were observed when the ionophore was added to the medium. The mechanism that limits the rate of calcium transport through the enamel organ during the secretory phase of enamel development is thus ATP-dependent. The result is consistent with the Takano-Crenshaw hypothesis for transcellular calcium transport. Use of the calcium ionophore A23187 failed to define further the nature of the calcium transport mechanism.