Identification of endothelin receptors in normal and hyperplasic human prostate tissues

Specific endothelin-1 (ET1) binding sites have been demonstrated in membranes derived form normal (NP) and benign hyperplasic (BPH) human prostate using an 125I-ET1 binding assay. 125I saturation experiments and Scatchard analysis demonstrated the existence of a homogeneous population of binding sites with high affinity (Kd(app)) and density (B(max)), respectively, 106 +/- 15 pM and 1086 +/- 399 fmol/mg protein for NP (n = 5) and 168 +/- 26 pM and 964 +/- 445 fmol/mg protein for BPH (n = 5). We demonstrated the presence of two subtypes of ET1 receptors, ETA and ETB, by means of the following ET1 competitors: ET2, ET3, and BQ123 (which is selective for the ETA receptor), and IRL1620 and sarafotoxine c (S6c) (which are selective for the ETB receptor). The displacement curves allowed us to conclude that the large majority (85%) of the ET1 receptors in normal and hyperplasic human prostate are of the A subtype.