The long-range goals of this project are to clarify the functions of the specific stages of the ameloblast and to determine the roles of the cell membranes and their specializations in controlling calcium transport in relation to mineralization. An animal model system, including systemic and local application of experimental agents through surgical windows over ameloblasts in rat mandibles, will be utilized. The hypotheses to be tested are: (1) Specific regions of ameloblast cell membranes control translocation of calcium along or within the membranes and between the extracellular and intracellular compartments. Variation in distribution of enzymes and other membrane constituents, calcium channels, specializations such as the ruffled border; and junctional complexes serve as important control mechanisms in this process. (2) Morphologic types of maturation ameloblasts (smooth and ruffle-ended) reflect specializations in routes of absorption and processing of organic elements of enamel. The following experimental agents will be utilized: calcium antagonists cobalt, verapamil, lanthanum and tetracaine; Ca+2-Mg+2 ATPase inhibitors quercetin and ethacrynic acid; the hormone calcitonin; the anti-microtubular agent colchicine; and sodium fluoride. A multi-method analysis will be applied using light and electron microscopy, autoradiography, cytochemistry, and elemental microanalysis to determine the effects of these agents and to correlate the results with the postulated hypotheses. The proposed experiments are significant for clarifying the basic mechanisms involved in cellular control of calcium transport and the roles of the morphologic types of ameloblasts in enamel formation. The results of this proposal have implications for therapeutic and preventative measures against diseases involving mineralized tissues.
