Adrenoceptor Function and Expression in Bladder Urothelium and Lamina Propria

OBJECTIVE To investigate the role of adrenoceptor subtypes in regulating the spontaneous contractile activity of the inner lining of the urinary bladder (urothelium/lamina propria). MATERIALS AND METHODS The responses of isolated strips of porcine urothelium/lamina propria to noradrenaline, phenylephrine, and isoprenaline were obtained in the absence and presence of receptor subtype-selective antagonists. Quantitative reverse-transcriptase polymerase chain reaction was undertaken to assess the expression of adrenoceptor genes. RESULTS The tissues expressed all alpha(1)-and beta-adrenoceptor subtypes, with the alpha(1A)-, alpha(1B)-, and beta(2)-adrenoceptors the predominant receptors at the messenger RNA level. In the functional experiments, the rate of phasic contractions and the basal tension were increased by the alpha(1)-adrenoceptor agonists phenylephrine (100 mu M) and A61603 (10 mu M). The rate and tension responses to phenylephrine were reduced by low concentrations of tamsulosin (3 nM) and RS100329 (10 nM) but were unaffected by BMY7378 (100 nM), prazosin (10 nM), and RS17053 (1 mu M). In contrast, isoprenaline and salbutamol (both 1 mu M) induced a relaxation of tissues and slowing of phasic contractions. The rate and tension responses to isoprenaline were inhibited by propranolol (100 nM) or a combination of CGP20712A (30 nM) and ICI118551 (70 nM). The rate responses were also significantly inhibited by ICI118551 alone (70 nM). CONCLUSION Although all alpha(1)-and beta-adrenoceptor subtypes were expressed in the pig urothelium/lamina propria, the alpha(1A/L)-adrenoceptor appeared to mediate increases in the contractile rate and tension. The beta-adrenoceptor induced inhibition of spontaneous contractile activity appears to be predominately mediated by beta(2)-adrenoceptors, with beta(1)-and beta(2)-adrenoceptors possibly involved in the tension responses. UROLOGY 81:211.e1-e211.e7, 2013. (C) 2013 Elsevier Inc.