Demonstration of .ALPHA.1-adrenoceptors in human hypertrophied prostate with tritiated bunazosin.

Abstract

The α1-adrenoceptor is considered to regulate micturition in patients with benign prostatic hypertrophy. This study demonstrated the specific binding sites of [3H]-bunazosin hydrochloride (4-amino-2-2-[4-butanoyl-hexahydro-1H-1, 4-diazepin-1-yl]-6, 7-dimethoxy quinazoline hydrochloride) in the large sections of the prostate. Eleven surgical specimens of en bloc retropubic prostatectomy were evaluated by in vitro receptor autoradiography. Autoradiograms were assessed using a computerized image analysis system to locate the specific binding sites. Suitable specimens were coated with emulsion for microautoradiography. Specific binding sites were recognized mainly in the perinodular regions of the prostate as well as in some nodules and in the urethral region. Silver grains were recognized in the fibromuscular stroma of the perinodular and subepithelial regions of the prostatic ducts and acini. Some epithelial cells and the basement membrane of the ducts, the acini, and the prostatic urethra also revealed the accumulation of silver grains. Whether this latter finding indicated specific binding to α1-adrenoceptors or not is a matter for further investigation. This study indicated that [3H]-bunazosin was useful for the qualitative demonstration of specific α1-adrenoceptor binding sites in the prostate by in vitro receptor autoradiography.