The first phase of research involves the characterization of calcium-dependent signal transduction in ovarian steroidogenic cells. Specific pharmacological drugs, such as calcium channel blockers, calcium ionophores and calmodulin inhibitors, will be used in in vitro static incubation of ovarian tissue to elucidate the role of specific components in calcium signaling pathways regulating ovarian steroid production. A primary cell culture system will be developed for Atlantic croaker ovarian steroidogenic cells to directly measure changes in intracellular calcium concentrations in response to hormone treatments. The second phase of research will investigate xenobiotic disruption of calcium-dependent signal transduction and subsequent alteration of ovarian steroidogenesis. Preliminary experiments will study effects of xenobiotic chemicals on normal endocrine function by screening a variety of compounds including heavy metals, pesticides, and polychlorinated biphenyls (PCBs). Compounds causing significant alteration in steroid production in the preliminary assays will be selected for continued experiments to elucidate whether the chemical is altering endocrine function by modifying calcium-dependent signal transduction. In vitro ovarian tissue incubations will be used to assess effects of contaminants on ovarian steroidogenesis, and ovarian steroidogenic cells in primary culture will be used to determine direct effects of xenobiotics on calcium homeostasis.