Studies of the effects of fluoroacetate on ameloblasts in rat incisor.

The effects of fluoroacetate on the ameloblasts were studied in the rat incisor. Fluoroacetate is an inhibitor of tricarboxylic acid cycle and accumulation of citrate occurred in the animal tissues due to fluoroacetate administration. In the present study, fluoroacetate injection caused severe morphologic changes in the ameloblasts. The most prominent change was observed in the mitochondria. Reduction of the mitochondrial matrix density was the earliest change followed by varying degrees of matrix swelling. Loss of the matrix granules and disintegration of the cristae were also observed. The difference in the mitochondrial activities in regard to the citrate metabolism was found between the matrix formation stage and the maturation stage in the ameloblasts. Extensive dilatation of the rough-surfaced endoplasmic reticulum and grossly enlarged vacuoles were found mainly in the early maturation stage at 12 and 24 hours after the fluoroacetate administration. These abnormally large vacuoles seemed to be caused by the water stored within the endoplasmic reticulum cisternae. Accumulation of plasma citrate and decrease of ionized calcium concentration in the whole blood were observed in the fluoroacetate treated group. These findings suggest that fluoroacetate may cause the lowering of the function of the ameloblasts through the suppression of cell energy production and that both the secretion of the matrix and the calcification of the enamel may be inhibited.