Chronic Cd exposure results in renal proximal tubular (PT) cell damage. Delivery of Cd to the kidney occurs mainly as complexes with metallothionein-1 (MT-1) (MW~7kDa), freely filtered at the glomerulus. For Cd to gain access to the PT cells, these complexes are thought to be internalized via receptors for small protein ligands such as megalin, followed by release of Cd from MT-1 in endo-/lysosomal compartments. To investigate the role of megalin in renal Cd7MT-1 reabsorption, we studied megalin expression as well as megalin dependence of Cd7MT-1 uptake and cytotoxicity in a renal PT cell model (WKPT-0293 Cl.2 cells). Megalin expression in PT cells was detected by RT-PCR, and visualized by immunocytochemistry both at the cell surface (life staining) and intracellularly (permeabilized cells). AlexaFluor®488-coupled MT-1 was taken up into PT cells in a concentration dependent manner, saturating at about 15mM. At 14.1mM, this MT-1 uptake could be significantly attenuated by 30.9±6.6% (n=4) by 1mM of the receptor-associated protein RAP used as a competitive inhibitor of megalin binding. Consistently, cytotoxicity of a 24h treatment with 7.14mM Cd7MT-1 was significantly reduced by 41.0±7.6% and 61.6±3.4% (n=5 each) by the presence of 1mM RAP or 400mg/ml anti-megalin antibody, respectively. These data indicate that renal Cd7MT-1 uptake is mediated at least in part by megalin.