[Effects of microtubule inhibitors on the amelogenesis in rat incisor enamel at the maturation stage: changes of staining patterns of GBHA on the enamel surface].

We investigated the effect of microtubule inhibitors on the amelogenesis in rat incisor enamel at the maturation stage by the glyoxal bis (2-hydroxyanil) (GBHA) staining method. Several red stripes stained with GBHA appeared on the maturation enamel surface of control rats. Colchicine injection (1.3 mg/kg, s.c.) disarranged the GBHA staining stripes and increased the staining area. The ratio of the GBHA staining area to the maturation enamel surface was about 25% in the control, but this value increased about 60% at 8 and 24 hr after the colchicine injection. Lumicolchicine, which does not have the ability to disrupt microtubules, did not cause any significant changes in the enamel surface. The incorporation of 45Ca to the maturation enamel was also reduced by colchicine. Since the hypocalcemic action of microtubule inhibitors may be related to the change of the enamel surface, other drugs, sodium salicylate and sodium fluoride, that have a hypocalcemic action were tested. The staining pattern was not altered by these drugs. Therefore, the hypocalcemic action was independent of the changes of the GBHA staining pattern. These results indicated that the disruption of microtubules in the ameloblasts inhibited calcium movement in the maturation enamel, resulting in the disarrangement of the GBHA staining pattern.