Urol Res (1997) 25:19%206 © Springer-Verlag 1997 M. Goepel-A. Wittmann-H. Riibben. M.C. Michel Comparison of adrenoceptor subtype expression in porcine and human bladder and prostate Received: 31 July 1996/Accepted: 16 October 1996 Abstract We have quantified and characterized 0tl- , ~2- and 13-adrenoceptor subtypes in porcine bladder de- trusor and bladder neck, human bladder detrusor, and porcine and human prostate. ~1-, a2- and 13-ad- renoceptor were identified in radioligand binding studies using [3H]prazosin, [3H]RX 821002 and [125I]io- docyanopindolol, respectively, as the radioligands. In porcine male and female detrusor and bladder neck and male prostate, adrenoceptors were detected in the order of abundance 13 > ~2 >> ~1 (not detectable), with no major differences between the sexes or between detrusor and bladder neck. In human detrusor and prostate the order of abundance was 13 > ~2 )) 0~1 (not detectable) and 13>> ~1 > ~2, respectively. The ~2-adrenoceptors in all tissues were homogeneously of the ~2A-Subtype as evidenced by competition binding studies with yohimbine, prazosin, ARC 239 and oxymetazoline. The 13-adrenoceptors represented a mixed population with a dominance of the 13z-subtype in all tissues as demon- strated by competition binding with ICI 118,551 and CGP 20,712A. We conclude that pigs may be a suitable model for studies of detrusor function with respect to adrenoceptor expression. They may be less suitable for studies of bladder neck or prostate function. Key words Pig - Human • a2-Adrenoceptor - 13-Adrenoceptor • Bladder. Prostate Introduction Urinary incontinence and other forms of disturbed mi- cturition are a major cause of morbidity which may gain even greater importance with the growing portion of the elderly in the population [20]. Normal bladder function M. Goepel ([~). H. Riibben Department of Urology, University of Essen Medical School, Hufelandstr. 55, D-45t22 Essen, Germany A. Wittmann. M.C. Michel Department of Medicine, University of Essen, Essen, Germany depends on a coordinated balance between pressure developed by the detrusor muscle and resistance devel- oped by the bladder neck, the urethra and, in males, the prostate. In the filling phase relaxation of the detrusor and contraction of the sphincters are required, while in the micturition phase contraction of the detrusor and relaxation of the sphincters are necessary. This is coor- dinated by the integration of excitatory, inhibitory and sensory nerves in control centers in the spinal cord and brain [7]. While contraction of the detrusor muscle is mainly controlled by cholinergic mechanisms [1], sym- pathetic pathways may also contribute to the regulation of detrusor tone and possibly even more importantly may be involved in the control of resistance of the lower urinary tract [1]. The sympathetic nervous system acts on three classes of receptors (~, ~2 and 13) with at least three subtypes each which are designated ala, alB, C*1I~, aaA, aZC, 131,132 and 133 [3, 10]. At the neuroeffector junction between sympathetic nerves and smooth muscle cells, ~1- and ~2- adrenoceptors generally mediate enhancements of con- traction, while 13-adrenoceptors mostly mediate smooth muscle relaxation; prejunctional c,2-adrenoceptors may additionally attenuate smooth muscle contraction by inhibiting the release of contraction-causing neuro- transmitters. Such observations have also been made in smooth muscle of urogenital tissues [1]. While recent research has accumulated large amounts of information regarding expression of al-adrenoceptor subtypes in the human prostate [12, 17, 22], only limited information is available on subtypes of other adrenoceptors in the prostate and on subtypes of all types of adrenoceptors in the bladder. Advances in physiological and pathophysiological knowledge on micturition will require the use of adequate animal models. An optimal animal model should not only be large enough to allow detailed urodynamic measure- ments and have sufficient anatomical similarity with hu- mans but should also exhibit a similar profile of receptor subtype expression. Therefore, we have compared ex- pression of subtypes of ~1-, ~2- and [3-adrenoceptors in