Comparison of adrenoceptor subtype expression in porcine and human bladder and prostate

We have quantified and characterized alpha 1-, alpha 2- and beta-adrenoceptor subtypes in porcine bladder detrusor and bladder neck, human bladder detrusor, and porcine and human prostate. alpha 1-, alpha 2- and beta-adrenoceptor were identified in radioligand binding studies using [3H]prazosin, [3H]RX 821002 and [125I]iodocyanopindolol, respectively, as the radioligands. In porcine male and female detrusor and bladder neck and male prostate, adrenoceptors were detected in the order of abundance beta > alpha 2 >> alpha 1 (not detectable), with no major difference between the sexes or between detrusor and bladder neck. In human detrusor and prostate the order of abundance was beta > alpha 2 >> alpha 1 (not detectable) and beta >> alpha 1 > alpha 2, respectively. The alpha 2-adrenoceptors in all tissues were homogeneously of the alpha 2A-subtype as evidenced by competition binding studies with yohimbine, prazosin, ARC 239 and oxymetazoline. The beta-adrenoceptors represented a mixed population with a dominance of the beta 2-subtype in all tissues as demonstrated 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.