Effect of cobalt on Ca2+-Mg2+ ATPase in rat incisor maturation ameloblasts.

Rat incisor maturation ameloblasts were studied to determine the effect of injected cobalt on the distribution and intensity of Ca2+-Mg2+ ATPase. The dosage of cobalt utilized temporarily inhibits enamel mineralization and alters ameloblast-associated calcium. A modified Wachstein-Meisel medium containing cerium as the capturing ion was used to localize Ca2+-Mg2+ ATPase cytochemically. The distribution and intensity of the reaction product in normal maturation ameloblasts was, as previously reported, primarily in association with the plasma membranes. The lateral cell membranes of both smooth-ended and ruffle-ended ameloblasts were reactive. The ruffled border region contained the heaviest concentration of reaction product. Although cobalt did not alter the general pattern of distribution of the reaction product in either cell type, in all regions of activity the intensity was noticeably increased. Cells modulating from smooth-ended to ruffle-ended ameloblasts and under the influence of cobalt exhibited an irregular dense layer along the enamel surface, and large focal accumulations of electron-dense material in the various extracellular compartments. This may indicate interference with a putative resorptive activity of these cells.