This project will inform a systems biology platform for identifying adverse responses to environmental compounds on testicular development in mice, a commonly used model system in the field of Toxicology. In order to validate the organotypic culture system, we have investigated the adverse effects of the known testicular toxicant, cadmium. To initiate the culture model, we isolate and plate testicular cells from immature mice on postnatal day (PND) 9 in order to capture a developmental window of susceptibility. Based on a literature search derived developmental timeline, we chose to treat the culture on days in vitro (DIV) 2, 5 and 15 with cadmium and quantify effects 24 hours later. We hypothesized that dosing with cadmium during these time points would correspond to impacts on steroid regulation, proliferation, and spermatogenesis processes. In order to evaluate a dose response relationship in our testicular culture, we treated the testis cells with 2.5, 5.0 and 10 uM concentrations of cadmium. To quantify the effects of cadmium in our cell culture model we evaluated; total protein, testosterone production, cell type specific proteins with western blots, LDH cytotoxicity, 3 color assay for live and dead cells and immunofluorescence to capture morphology for DIV 3,7 and 16, 24 hours post treatment for all three doses. Our initial studies have observed that cadmium treatment for all three doses impacted testosterone production, germ cell morphology and proliferation on DIV 7 and 16.