The α1C‐adrenoceptor in human prostate: cloning, functional expression, and localization to specific prostatic cell types

Abstract

Benign prostatic hyperplasia (BPH) causes urinary obstruction in aging men that frequently requires surgery to relieve the symptoms of urinary retention, nocturia, and micturition. Smooth muscle tone which contributes to the urethral constriction in the enlarged gland appears to be mediated by the α1‐ adrenoceptors. In this paper, molecular and pharmacological approaches are used to establish the role played by the α1c‐adrenoceptor subtype in the prostate. The α1‐adrenoceptor subtype(s) expressed in human prostate were investigated by use of polymerase chain reaction (PCR), Northern blot, and in situ hybridization. The α1C subtype was found in both prostate stromal and glandular cells while α1B and α1D subtypes were expressed in glandular cells. High expression levels for α1C were observed in prostate cancer tissues in both stroma and glandular cells. Full length α1C‐adrenoceptor cDNA was cloned from human prostate. Stable mammalian cell lines expressing human α1B‐, α1C‐, and α1D‐adrenoceptors were made. Membranes prepared from these cell lines and human prostate were used to evaluate the pharmacological profiles of human α1B‐, α1C‐ and αD‐adrenoceptors in comparison to human prostate. Leverage plot analysis of compound affinities determined by competition for [125I]‐I‐HEAT binding demonstrated that the αlC subtype is the predominant α1‐adrenoceptor in human prostate. The α1‐adrenoceptors cause smooth muscle constriction by coupling to IP3 turnover and intracellular Ca2+ release. Using stable cell lines to measure IP3 production in response to noradrenaline, α1C stimulated IP3 production most efficiently, with α1B at an intermediate level, while little IP3 above background could be detected with αD. These results supported a functional role of the α1C‐adrenoceptor on prostate smooth muscle constriction by noradrenaline stimulation. 1995 British Pharmacological Society