EPIDERMAL GROWTH-FACTOR PRECURSOR IS PRESENT IN A VARIETY OF HUMAN RENAL CYST FLUIDS

Progressive human renal cystic diseases are characterized by prolifera tion of the epithelial cells lining the cyst. The kidney synthesizes e pidermal growth factor and its presence in renal cyst fluid might cont ribute to renal epithelial cell proliferation. We screened autosomal d ominant polycystic kidney disease, acquired renal cystic disease, the von Hippel-Lindau syndrome, multilocular cystic nephroma, multicystic dysplastic kidney disease and simple cyst fluids for the presence of e pidermal growth factor by radioreceptor assay, specific radioimmunoass ay, immunoprecipitation and immunoblotting. Multiple epidermal growth factor immunoreactive species of approximately 180 kD. and lower molec ular weights were present in almost all cyst fluids examined, suggesti ng endogenous synthesis and limited proteolysis of epidermal growth fa ctor precursor protein in cyst fluid. Tamm-Horsfall protein was detect ed by enzyme-linked immunosorbent assay in most cysts (for example 55 of 59 autosomal dominant polycystic kidney disease samples). The major ity of simple and autosomal dominant polycystic kidney disease renal c ysts contained high sodium ion concentration, epidermal growth factor precursor protein and Tamm-Horsfall protein, characteristic of the ear ly thick ascending limb. Rather than the mere presence of epidermal gr owth factor in renal cyst fluids, increased sensitivity to epidermal g rowth factor or other mitogens present in renal cyst fluid may be path ogenic in progressive renal cystic disease.