Cadmium is a pollutant that occasions significant concern and investigation because of the ubiquitous and persistent nature of human exposure and because the level of Cd in humans is often well within an order of magnitude of that which elicits overt toxic effects. Despite very extensive human, animal and cellular studies, large uncertainties remain regarding the risks posed by current human burdens of this element. Elucidation of the ways in which, and of the molecular mechanisms by which cells respond to cadmium are a necessary component of efforts to reduce these uncertainties. Definition of the effects of cadmium on cell growth, especially as mediated through effects on expression of genes (including oncogenes) involved in regulation of cell growth and differentiation, should aid significantly in defining the carcinogenic and teratogenic potential of this element. Previous studies showed that Cd++ and transforming growth factor beta (TGF beta) both stimulate a delayed mitogenic response in NRK- 49F cells and stimulate soft agar growth of Balb/c 3T3. Cd++ at subtoxic levels waS also shown to modulate epidermal growth factor (EGF)-induced DNA synthesis in NRK-49F cells. These observations raise two important questions. First, to what extent does Cd++ affect or effect the full spectrum of growth factor-induced cell responses? Second, what are the possible mechanisms by which Cd++ elicits these responses? Do Cd++ and/or TGF beta, for example, elicit a delayed DNA synthesis response in NRK-49F by inducing a platelet derived growth factor (PDGF) mediated autocrine growth factor response? To address these questions, this project will determine the ways in which Cd++, EGF and TGF beta alone and in combination elicit and/or modulate growth and growth related metabolic processes in NRK-49F cells by: (1) Measuring the effects of these factors on glycolysis, amino acid and glucose uptake, and RNA and protein synthesis rates; (2) Following increases in cell mass as induced by these factors; relating these to DNA synthesis and mitosis to determine whether balanced growth occurs; (3) Defining the effects of these factors on genes whose expression is related to cell growth or response to cell growth factors (action, sis, fos, myc, JE, KC); (4) Delimiting the ways in which these factors may modulate the extracellular matrix by following the appearance in the extra cellular matrix and in cell culture medium of secreted matrix proteins, proteases and protease activators and inhibitors; (5) Testing the effects of Cd++ and TGF beta on EGF binding, of Cd++ and EGF on TGF beta binding, and of TGF beta and EGF on Cd++ uptake and accumulation.
