Autonomic Receptors in Human Prostate Adenomas

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Abstract
Radioligand receptor binding techniques were used to characterize alpha1 adrenergic, alpha2 adrenergic and muscarinic cholinergic (MCh) binding sites in human prostate adenomas obtained from men with symptomatic and asymptomatic benign prostatic hyperplasia (BPH). Prostate adenoma specimens were obtained from nine men with asymptomatic BPH undergoing cystoprostatectomy, 11 men with symptomatic BPH undergoing open prostatectomy, and 11 men with symptomatic BPH undergoing transurethral resection of the prostate (TURP). A quantitative symptoms score analysis and urinary flow rate determinations documented the absence of bladder outlet obstruction in men undergoing cystoprostatectomy and confirmed the presence of bladder outlet obstruction in men undergoing prostatectomy. The mean equilibrium dissociation constants (Kd) and the mean densities of 125I-Heat (alpha1 adrenergic) and 3H-NMS (MCh) binding sites were similar in tissue homogenates obtained from men with asymptomatic and symptomatic BPH. The mean Kd of 3H-Rauwolscine (3H-Ra) was significantly greater in the prostatectomy specimens obtained from men with symptomatic BPH compared to the specimens obtained from men with asymptomatic BPH (p < 0.05). The density of 3H-Ra (alpha2 adrenergic) binding sites was significantly greater in the prostate adenomas obtained from men with symptomatic BPH compared to the prostate adenomas obtained from men with asymptomatic BPH (p < 0.05). The difference in alpha2 adrenoceptor density was accounted for by an increased receptor density in the open prostatectomy specimens. There was no significant correlation between alpha2 adrenergic, alpha1 adrenergic, and MCh receptor densities and prostate weight or patient age. This study indicates that the development of infravesical obstruction in men with BPH is not related to upregulation or altered binding affinity of alpha1 adrenergic or MCh receptor binding sites. The significance of the observed upregulation of alpha2 adrenoreceptors in the prostate adenomas obtained from men undergoing open prostatectomy is unknown, and requires further investigation.