β-Adrenoceptor subtypes in the ureteral smooth muscle of rats, rabbits and dogs

We investigated the β-adrenoceptor subtypes mediating ureteral relaxation in rats, rabbits and dogs. The relaxing effects of β-adrenoceptor agonists were evaluated on KCl-induced ureteral contractions. The rank order of potency of the catecholamines tested was isoprenaline>noradrenaline>adrenaline in rat ureter; isoprenaline>adrenaline>noradrenaline in rabbit ureter; only isoprenaline was effective in canine tissues. The β 1-adrenoceptor agonist, dobutamine, produced relaxation of rat ureter. The β 2-adrenoceptor agonist, procaterol, produced more significant relaxation of rabbit ureter than did dobutamine. CL-316243 [( R, R)-5-[2-[[2-(3-chlorophenyl)-2-hydroxyethylamino]propyl]-1,3-benzodioxole-2,2-dicarboxylate] and CGP-12177A [(±)[4-[3[(1,1-dimethylethyl)amino]-2-hydroxypropoxy]-1,3-dihydro-2 H-benzimidazol-2-one hydrochloride], β 3-adrenoceptor agonists, were more effective in relaxing canine ureter than were dobutamine and procaterol. Isoprenaline-induced relaxation was antagonized by a β 1-adrenoceptor antagonist, CGP-20712A [2-hydroxy-5(2-((2-hydroxy-3-(4-((1-methyl-4-trifluoromethyl)1 H-imidazole-2-yl)phenoxy)propyl)amino)ethoxy)-benzamide monomethane sulphonate], in rats and by a β 2-adrenoceptor antagonist, ICI-118,551 [(±)-1-[(2,3-dihydro-7-methyl-1 H-inden-4-yl)oxy]-3-[(1-methylethyl)amino]-2-butanol hydrochloride], in rabbits. The non-selective β-adrenoceptor antagonist, bupranolol, antagonized isoprenaline-induced relaxation in all species tested. In conclusion, β-adrenoceptor agonists may relax ureter by stimulating mainly β 1-adrenoceptors in rats, β 2-adrenoceptors in rabbits and mainly β 3-adrenoceptors in dogs.