High affinity binding sites for epidermal growth factor (EGF) in renal membranes

The kidney produces large quantities of EGF but the role of the kidney in binding and degradation of EGF is unknown. We studied 125I-EGF binding and degradation by highly purified cortical luminal and cortical basolateral membranes of rabbit renal cortex, and by medullary plasma membranes. Specific binding for 125I-EGF was found for the first time in cortical basolateral and medullary plasma membranes (60-80% of total binding) but not in cortical luminal membranes. There was little degradation (less than 4%) of EGF by any of the membranes. Scatchard analysis of 125I-EGF binding by cortical basolateral membranes revealed two distinct classes of binding sites: high and low affinity. The existence of high specific binding sites in cortical basolateral and in medullary plasma membranes suggests a physiologic role of EGF in the kidney.