Transporters function in cellular influx and efflux to maintain homeostasis for normal cellular and tissue physiology. Therefore, they play an important role in eliminating xenobiotics from the body. Areas of transporter research at the Graduate Center for Toxicology include characterization of the function and regulation of expression of the organic anion transporters, particularly the ATP-Binding Cassette (ABC) efflux transporters that mediate the cellular efflux of glutathione and glucuronide conjugates of endo- and xenobiotics; the role of the MRP1 transporter in protecting the cardiovascular system during certain cancer chemotherapy, such as doxorubicin therapy; the biological role of multidrug resistance proteins (MRPs) in cellular metabolism and detoxification; and the role of MRP1 in hematopoietic stem cell self-renewal. Receptors are critical in regulating gene expression, xenobiotic metabolism, and organism development. Receptor research at the Graduate Center for Toxicology involves structure-function studies of the retinoid X receptor. Another objective of this research is to develop selective agonists or antagonist compounds for this receptor for biotechnology applications.