AIMS: To investigate the role of beta-adrenoceptor subtypes in mediating relaxation of the pig bladder trigonal muscle in vitro. MATERIALS AND METHODS: Longitudinal strips of trigonal muscle were isolated, and the mucosa and serosa removed. Tissues were precontracted with KCl, and beta-adrenoceptor agonists (isoprenaline or salbutamol) were added cumulatively, and concentration-relaxation curves (CRCs) were obtained. CRCs to agonists were obtained in the absence and presence of antagonists and antagonist affinity values were calculated. RESULTS: Isoprenaline (non-selective beta-agonist) relaxed with high potency (pEC(50) = 7.2). Propranolol antagonized CRCs to isoprenaline with a high affinity (apparent pK(B) = 8.8), but the Schild plot had a slope significantly (P < 0.01) less than unity (0.61), suggesting that responses were mediated by more than one beta-adrenoceptor subtype. CGP20712A (beta(1)-antagonist) antagonized responses to isoprenaline with a low affinity (apparent pK(B) = 5.13), indicating beta(1)-adrenoceptors did not participate in the response. The affinity of ICI118551 (beta(2)-antagonist) for antagonism of responses to isoprenaline was also relatively low (apparent pK(B) = 6.9), and the Schild slopes were significantly (P < 0.01) less than unity (0.58). SR59230A (beta(3)-antagonist) antagonized CRCs to isoprenaline with a relatively low affinity (apparent pK(B) = 7.5), and with a Schild slope significantly (P < 0.01) less than unity (0.86), indicating that responses may be mediated by more than one beta-adrenoceptor subtype. In contrast to that observed with isoprenaline, the beta(2)-adrenoceptor selective agonist salbutamol induced relaxation with a relatively low potency (pEC(50) = 6.6) and with maximum responses of 80% of that to isoprenaline. ICI118551 competitively antagonized (Schild plot of unity) responses to salbutamol with a high affinity (pA2 = 8.3). CONCLUSIONS: These data suggest that beta-adrenoceptor mediated responses to isoprenaline of the bladder trigone are mediated via both the beta(2)- and beta(3)-adrenoceptor subtypes whilst responses to salbutamol appear to be mediated only via the beta(2)-adrenoceptor. Copyright 2003 Wiley-Liss, Inc.
AIMS: To investigate the role of beta-adrenoceptor subtypes in mediating relaxation of the pig bladder trigonal muscle in vitro. MATERIALS AND METHODS: Longitudinal strips of trigonal muscle were isolated, and the mucosa and serosa removed. Tissues were precontracted with KCl, and beta-adrenoceptor agonists (isoprenaline or salbutamol) were added cumulatively, and concentration-relaxation curves (CRCs) were obtained. CRCs to agonists were obtained in the absence and presence of antagonists and antagonist affinity values were calculated. RESULTS:Isoprenaline (non-selective beta-agonist) relaxed with high potency (pEC(50) = 7.2). Propranolol antagonized CRCs to isoprenaline with a high affinity (apparent pK(B) = 8.8), but the Schild plot had a slope significantly (P < 0.01) less than unity (0.61), suggesting that responses were mediated by more than one beta-adrenoceptor subtype. CGP20712A (beta(1)-antagonist) antagonized responses to isoprenaline with a low affinity (apparent pK(B) = 5.13), indicating beta(1)-adrenoceptors did not participate in the response. The affinity of ICI118551 (beta(2)-antagonist) for antagonism of responses to isoprenaline was also relatively low (apparent pK(B) = 6.9), and the Schild slopes were significantly (P < 0.01) less than unity (0.58). SR59230A (beta(3)-antagonist) antagonized CRCs to isoprenaline with a relatively low affinity (apparent pK(B) = 7.5), and with a Schild slope significantly (P < 0.01) less than unity (0.86), indicating that responses may be mediated by more than one beta-adrenoceptor subtype. In contrast to that observed with isoprenaline, the beta(2)-adrenoceptor selective agonist salbutamol induced relaxation with a relatively low potency (pEC(50) = 6.6) and with maximum responses of 80% of that to isoprenaline. ICI118551 competitively antagonized (Schild plot of unity) responses to salbutamol with a high affinity (pA2 = 8.3). CONCLUSIONS: These data suggest that beta-adrenoceptor mediated responses to isoprenaline of the bladder trigone are mediated via both the beta(2)- and beta(3)-adrenoceptor subtypes whilst responses to salbutamol appear to be mediated only via the beta(2)-adrenoceptor. Copyright 2003 Wiley-Liss, Inc.
Authors: L Ragionieri; M Botti; F Gazza; C Sorteni; R Chiocchetti; P Clavenzani; L Bo Minelli; R Panu Journal: Eur J Histochem Date: 2013-05-06 Impact factor: 3.188
Authors: V W Nitti; V Khullar; P van Kerrebroeck; S Herschorn; J Cambronero; J C Angulo; M B Blauwet; C Dorrepaal; E Siddiqui; N E Martin Journal: Int J Clin Pract Date: 2013-05-21 Impact factor: 2.503