Frozen ultrathin-sections for x-ray microanalysis of rat tooth germs.

In order to detect the precise location and pathways of calcium in the ameloblastic layer with EM and EDX, frozen ultrathin-sections, potassium pyroantimonate (PPA) method and 45Ca-autoradiography (A.R) were employed. A population of dense granules containing Ca and P was mainly observed within the nuclei and mitochondria of the frozen-sectioned ameloblasts, whereas PPA-reaction was seen not only within them but in ER, Golgi vesicles and intercellular spaces. No granules were found at the enamel matrix by both methods, but peaks for Ca and P were distinct. Silver grains of 45Ca-A.R were located in nuclei, mitochondria. Golgi complex and intercellular spaces. These results indicate that calcium can transport across the ameloblastic layer through two main pathways, extracellular and transcellular.