Cadmium toxicity is a continuing health concern for occupationally exposed workers in cadmium related industries and for the general public because of cadmium in industrial waste. Cadmium causes renal tubular dysfunction and abnormal bone formation and remodelling. Both clinical and experimental studies report direct effects of cadmium on bone. Complex interactions between cadmium and calcium are documented in the scientific literature. The mechanisms and toxicological significance of these interactions are not completely understood at this time. The goal of this application is to characterize cadmium-calcium interactions and the effects of cadmium on the second messenger functions of calcium under the working hypothesis: Cadmium perturbs, directly or indirectly, intracellular calcium homeostasis and calcium signal transduction pathways. The specific aims of the proposal are to: 1. Investigate intracellular cadmium metabolism in rat osteosarcoma cells (ROS) 17/2.8. Experiments will be conducted using 109Cd to characterize cadmium metabolism which will give insight into potential sites of Cd2+ toxicity within ROS cells. Sodium butyrate will be used to induce metallothionein and characterize changes in Cd2+ metabolism due to this induction. 2. Investigate the effects of cadmium on calcium homeostasis and epidermal growth factor modulation of calcium homeostasis. These experiments will be conducted using a) 19F nuclear magnetic resonance (NMR) studies in which the fluorinated Ca ion detector is 1,2-bis(2-amino-5-fluorophenoxy)ethane N,N,N',N'-tetraacetic acid (5F-BAPTA) to measure free intracellular Ca2+ ion concentration, and b) 45Ca to measure intracellular Ca2+ kinetic parameters and compartments, and intermediate (5-10 min) changes in Ca2+ efflux. 3.Examine Ca2+-Cd2+ interactions within a specific loci central to the Ca2+ messenger system, namely protein kinase Ca2+ activity. 4.Elucidate the mechanism of action by which cadmium decreases collagen synthesis, which is a calcium mediated process. These specific aims allow a focused, mechanistic approach for elucidating the effects of cadmium on calcium processes in bone at the cellular level. The results from this study should be broadly applicable for further understanding the role of cadmium in bone abnormalities and more generally the effects of cadmium on calcium mediated cell function.