Immunoreactive endothelin in the human kidney: comparison with natriuretic peptides. 
The presence of immunoreactive endothelin (IR-ET) was studied by radioimmunoassay in human kidney with and without clinical renal failure, and the levels were compared with those of three natriuretic peptides: atrial natriuretic peptide (ANP), brain natriuretic peptide (BNP), and C-type natriuretic peptide (CNP).  Kidney tissues were obtained at autopsy from three subjects with renal disorders (diabetic nephropathy, renal tubular necrosis, and end-stage kidney disease).  Normal renal tissue was obtained at surgery from two patients with renal cell carcinoma.  IR-ET was detected in three diseased kidneys obtained at autopsy (0.101 +/- 0.043 pmol/g wet weight, mean +/- SD) but not in tissues of two normal kidneys obtained at surgery (< 0.015 pmol/g wet weight).  Reverse-phase HPLC showed that most of the IR-ET in the kidney (> 90%) was eluted in the position of ET-1.  IR-ANP (0.23 +/- 0.06 pmol/g wet weight), IR-BNP (1.15 +/- 0.94 pmol/g wet weight), and IR-CNP (0.44 +/- 0.16 pmol/g wet weight) were detected in all samples examined.  Higher concentrations of IR-BNP were found in three diseased kidneys obtained at autopsy (1.70 +/- 0.83 pmol/g wet weight vs. mean in two normal kidney tissues, 0.32 pmol/g wet weight).  Such increases were not observed in IR-ANP or IR-CNP.  These findings indicate that IR-ET is present in the human diseased kidney even in end-stage disease, with high concentrations comparable to those of natriuretic peptides.  This raises the possibility that the production of ET-1 and BNP is increased in kidneys of patients with renal disorders.