Quantitative immunocytochemistry of Ca(2+)-Mg2+ ATPase in ameloblasts associated with enamel secretion and maturation in the rat incisor.

Our previous studies revealed intense membrane-associated labeling for Ca(2+)-Mg2+ ATPase (Ca(2+)-pump) in secretory and maturation ameloblasts in the rat incisor, both by enzyme cytochemistry and by immunohistochemical techniques. The purpose of the present study was to map the distribution of Ca(2+)-pump protein at the cellular and subcellular levels by means of a Ca(2+)-pump-specific monoclonal antibody and electron microscopic immunogold cytochemistry. Tissue specimens were dissected from secretory, early, and late enamel maturation zones. We quantified results by comparing gold particle densities over ameloblast lateral and distal plasma membrane regions, supranuclear cytoplasm, regions of the ruffled borders, and nuclei. The highest concentration of gold particles was seen over the distal membranes of early-maturation ameloblasts relative to those in late-maturation and secretory stages. Cytoplasmic labeling was less than that of the distal and lateral membranes, and gold particles located over nuclei were considered to be due to non-specific binding. These results are consistent with our earlier findings and suggest a role for the plasma membrane Ca(2+)-pump in the regulation of calcium availability to mineralizing enamel.