Contractile properties of human prostate adenomas and the development of infravesical obstruction

The contractile response of human prostate adenomas to KCl, phenylephrine (alpha 1 adrenergic agonist), UK 14304 (alpha 2 adrenergic agonist), and carbachol (muscarinic cholinergic agonist) was evaluated in tissue specimens obtained from men with symptomatic and asymptomatic BPH. Prostate specimens were obtained from 5 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). Quantitative symptom score analysis and urinary flow rate determination documented the absence of bladder outlet obstruction in men undergoing cystoprostatectomy and confirmed the presence of bladder outlet obstruction in men undergoing prostatectomy. The magnitude of the contractile response (Emax) and the potency of phenylephrine-induced contractions (EC50) in prostatic preparations obtained from men with symptomatic and asymptomatic BPH were similar. The IC50 for the inhibition of phenylephrine-induced contractions by prazosin was 3.2 nM, confirming that phenylephrine-induced contraction in the human prostate is mediated by the alpha 1 adrenoceptor. The contractile responses of prostate adenomas to muscarinic cholinergic and alpha 2 agonists were negligible. This study demonstrates that the development of bladder outlet obstruction in men with BPH is not related to alterations in the functional response of the smooth muscle component of the prostate adenoma.