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. 1999 Aug;127(7):1744-50.
doi: 10.1038/sj.bjp.0702709.

Pharmacological characterization of beta-adrenoceptors mediating relaxation of the rat urinary bladder in vitro

P A Longhurst  1 , M Levendusky
Affiliations

Pharmacological characterization of beta-adrenoceptors mediating relaxation of the rat urinary bladder in vitro

P A Longhurst et al. Br J Pharmacol. 1999 Aug.

Abstract

1. Isoproterenol relaxed KCl-precontracted rat bladder strips with a pD2 of 7.21 leaving a residual contractile response of 3.2% after 30 microM. The selective beta1-agonist, T-0509 (pD2 : 6.24, 10.1% residual contraction after 100 microM), beta2-agonist, terbutaline (pD2 : 5.43, 13.7% residual contraction after 100 microM), and beta3-agonists, BRL 37344A (pD2 : 6.60, 17.3% residual contraction after 100 microM), and SR 58611A (pD2 : 5.15, 34.0% residual contraction after 100 microM), also relaxed bladder strips. 2. The relaxant response to isoproterenol was weakly but significantly antagonized by 1 microM propranolol which produced a 3 fold shift of the concentration-response curve to the right, and significantly antagonized by the beta1-selective antagonist, metoprolol (10 microM, 3 fold shift), and the beta2-selective antagonist, butoxamine (100 microM, 6 fold shift). A combination of 10 microM metoprolol and 100 microM butoxamine caused a 15 fold shift of the concentration-response curve for isoproterenol to the right. Incubation with the beta3-antagonist, SR 59230A (1 microM), caused a 6 fold shift of the concentration response curve for isoproterenol to the right. 3. The non-conventional partial agonist, CGP 12177A, weakly relaxed KCl-precontracted bladder strips (pD2 : 3.31, 51.3% residual contraction after 300 microM); the relaxation was resistant to blockade by 1 or 10 microM propranolol. 4. In the presence of 200 microM propranolol, CGP 12177A (20 microM) or SR 59230A (10 microM) antagonized surmountably the relaxant effects of BRL 37344A. 5. The data suggest that rat urinary bladder body contains beta1, beta2, and beta3-adrenoceptors, all of which mediate relaxation.

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Figures

Figure 1
Figure 1
Responses of 40 mM KCl+4 mM CaCl2- or 5 μM carbachol-precontracted rat bladder body strips to time and to isoproterenol. Data are expressed as a percentage of the initial response to KCl or carbachol and maximal relaxation in the presence of pinacidil. Each point represents the mean±s.e.mean where N=6 and n=12.
Figure 2
Figure 2
Responses of KCl-precontracted rat bladder body strips to isoproterenol, T-0509, terbutaline, BRL 37344A, and SR 58611A. Data are expressed as a percentage of the initial response to KCl and maximal relaxation in the presence of pinacidil or cromakalim. Each point represents the mean±s.e.mean where N=19, n=67 for isoproterenol, and N=n=5 or 6 for the other agonists.
Figure 3
Figure 3
Responses of KCl-precontracted rat bladder body strips to cumulative addition of isoproterenol in the absence and presence of propranolol. The responses to isoproterenol before and after 30 min incubation in Krebs buffer containing vehicle (repeat) or 1 μM propranolol are shown. Data are expressed as a percentage of the initial response to KCl and maximal relaxation in the presence of cromakalim. Each point represents the mean±s.e.mean where N=5 and n=5–9.
Figure 4
Figure 4
Responses of KCl-precontracted rat bladder body strips to cumulative addition of isoproterenol in the absence and presence of SR 59230A. The responses to isoproterenol before and after 30 min incubation with 1 μM SR 59230A are shown. Data are expressed as a percentage of the initial response to KCl and maximal relaxation in the presence of pinacidil. Each point represents the mean±s.e.mean where N=9 and n=7–29.
Figure 5
Figure 5
Responses of KCl-precontracted rat bladder body strips to cumulative addition of isoproterenol after β1- and β2-blockade. The responses to isoproterenol before and after 30 min incubation with 10 μM metoprolol, 0.1 mM butoxamine, or 10 μM metoprolol plus 0.1 mM butoxamine are shown. Data are expressed as a percentage of the initial response to KCl and maximal relaxation in the presence of pinacidil. Each point represents the mean±s.e.mean where N=7 and n=5–27.
Figure 6
Figure 6
Responses of KCl-precontracted rat bladder body strips to cumulative addition of CGP 12177A. The responses to CGP 12177A before and after 30 min incubation with 1 μM or 10 μM propranolol are shown. Data are expressed as a percentage of the initial response to KCl and maximal relaxation in the presence of pinacidil. Each point represents the mean±s.e.mean where N=7 and n=6–21.
Figure 7
Figure 7
Responses of KCl-precontracted rat bladder body strips to cumulative addition of BRL 37344A after β1- and β2-blockade. The responses to BRL 37344A before and after 30 min incubation with 200 nM propranolol, 200 nM propranolol+20 μM CGP 12177A, and 200 nM propranolol+10 μM SR 59230A are shown. Data are expressed as a percentage of the initial response to KCl and maximal relaxation in the presence of pinacidil. Each point represents the mean±s.e.mean where N=6 and n=5 or 6.
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