The Influence of Vanadate on Calcium Uptake in Maturing Enamel of the Rat Incisor

Abstract

The influence of vanadate, a potent inhibitor of Ca²⁺-ATPase and Na⁺-K⁺-ATPase, on ⁴⁵Ca uptake in maturing enamel of the rat incisor was investigated by a vascular perfusion method combined with 45Ca autoradiography. The morphological integrity of the maturation-stage enamel organ was well-retained during vascular perfusion under all the experimental conditions. Distinct patterns of ⁴⁵Ca labeling, comparable with those found in previous in vivo ⁴⁵Ca autoradiographic studies, appeared in the maturing enamel after vascular perfusion with a standard perfusate. One mmol/L vanadate added to the standard perfusate caused a drastic decrease in ⁴⁵Ca uptake in the maturing enamel, corresponding to the ruffle-ended ameloblasts, leaving narrow peaks of moderate intensity corresponding to the bands of the overlying smooth-ended ameloblasts. The in vitro labeling of exposed enamel surfaces with ⁴⁵Ca revealed blackening of autoradiographic emulsion in wide bands separated by unlabeled or slightly labeled narrow ones resembling the distribution of smooth-ended ameloblasts in both control and vanadate-treated incisors.

Our observations indicate that the ruffle-ended ameloblasts of the rat incisor serve as an efficient diffusion barrier to calcium ions and regulate transcellular calcium transport to the maturing enamel, at least in part, by a vanadate-sensitive mechanism.

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