Absence of peripheral-type benzodiazepine binding sites in renal carcinoma: a potential biochemical marker.

In an attempt to identify a tumour marker, we investigated peripheral-type benzodiazepine binding sites (PBS) in kidney specimens obtained from patients who underwent nephrectomy due to a renal mass. [3H]PK 11195, an isoquinoline carboxamide derivative, was used as a ligand. Binding assays were conducted on samples of membrane homogenate taken from both the healthy portion and the tumour site of the kidney. It was found that binding characteristics of benign tumours and normal kidney tissues were not significantly different, i.e. equilibrium dissociation constants of 2.20 +/- 0.73 and 2.38 +/- 0.98 nM, respectively, and maximal number of binding sites of 3190 +/- 1081 and 4189 +/- 998 fmol/mg protein, respectively. In contrast, no PBS were detectable in renal carcinoma. The absence of PBS in malignant renal tissues may serve as a biochemical marker for tumours of the kidney.