The Effects of β-Adrenoceptor Agonists on KCI-induced Rhythmic Contraction in the Ureter of Guinea Pig

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In the present study, we tried to determine what effects were induced by β-adrenoceptor agonists on 40 mM KCl-induced rhythmic contraction and to clarify which β-adrenoceptor subtypes are involved in the regulation of ureter motility in the guinea pig by using in vitro functional analysis. 40 mM KCl-induced rhythmic contraction was abolished by papaverine(10^<-6>M), nicardipine(10^<-5>M)and cromakalim(10^<-5>), but was not influenced by atropine(10^<-6>M). Isoprenaline decreased the amplitude, and changed the pattern of 40 mM KCl-induced rhythmic contraction in concentration-dependent manner. These results suggest the possibility that the stimulation of β-adrenoceptors may regulate the ureteral peristalsis. Salbutamol(selective β_2-AR agonist)and CGP12177(β_<1, 2>-AR antagonist and β_3-AR partial agonist)were also effective in decreasing the amplitude and changing the pattern of the rhythmic contraction.The pD_2 values of agonists were 7.57(isoprenaline), 5.80(CGP12177)and 7.63(salbutamol), respectively. The concentration-response curves of isoprenaline and salbutamol were rightward shifted by the presence of propranolol, and the apparent pA_2 values for propranolol against isoprenaline and salbutamol were 7.12 and 6.29, respectively. These results suggest that inhibition for 40 mM KCl-induced rhythmic contraction of the ureter by isoprenaline and salbutamol mediated mainly via atypical β-adrenoceptor subtype.
日本平滑筋学会の論文