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

Abstract

We have quantified and characterized α₁-, α₂-and β-adrenoceptor subtypes in porcine bladder detrusor and bladder neck, human bladder detrusor, and porcine and human prostate. α₁-, α₂- and β-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 β > α₂ ≫ α₁ (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 β > α₂ ≫ α₁ (not detectable) and β ≫ α₁ > α₂. respectively. The α₂-adrenoceptors in all tissues were homogeneously of the α_2A-subtype as evidenced by competition binding studies with yohimbine, prazosin, ARC 239 and oxymetazoline. The β-adrenoceptors represented a mixed population with a dominance of the β₂-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.