Prolactin and luteinizing hormone‐releasing hormone receptors in human benign prostatic hyperplasia and prostate cancer

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Abstract
Using a sensitive micromethod for the determination of prolactin (PRL) binding sites based on 125I-human PRL ligand, PRL receptor levels in specimens of benign prostatic hyperplasia (BPH) and human prostate cancer were estimated by the one-point assay system. Ten of 19 BPH specimens (53%), showed significant PRL binding, four being in the 9–12 fmol/mg range. All ten of these cases had an histological diagnosis of nodular glandular hyperplasia. Of ten adenocarcinomas examined, four samples (40%) exhibited positive PRL binding, the highest receptor levels being 10.2 fmol/mg protein. To characterize the receptors from BPH membranes, samples were then separately pooled according to the results obtained in one-point assays. In the PRL-negative pool no displacement could be detected. In the PRL-positive pool, the Scatchard analysis revealed one class of receptors with an average affinity Kd = 1.1 × 10−9 M and capacity Bmax = 287 fmol/mg protein. In the prostate cancer specimens, luteinizing hormone-releasing hormone receptors with a high affinity and a low capacity were also found. The results indicate the presence of prolactin receptors in prostate cancer and in BPH. The clinical implications of such findings are not clear, but it is possible that a certain proportion of BPH and prostate cancers might be in part PRL dependent. Further studies are necessary to ascertain this hypothesis in an attempt to improve the treatment of BPH and prostate cancer.