The presence of a specific SOD surface membrane receptor in rat hepatocyte cells was investigated using ligand blot analysis of the SOD receptor with 125I-SOD, and binding studies with iodinated and fluorescinated SOD. A specific SOD receptor with a molecular weight of about 320 kDa was identified. We suggest that the modulatory role of SOD on HMG-CoA reductase is exerted through this specific receptor.