Identification of endothelin receptors in normal and hyperplasic human prostate tissues

Specific endothelin‐1 (ET1) binding sites have been demonstrated in membranes derived from 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 (Kdapp) and density (Bmax), 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. © 1996 Wiley‐Liss, Inc.