Determination of controlling factor of detrusor contraction in urothelium and the role of Rho Kinase

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The mRNA and protein expression of muscarinic receptor subtypes, adorenoceptor subtypes as well as RhoA/Rho kinase and its activity were investigated by radioligand binding experiments, realtime RT-PCR, Western blotting and immunohistochemistry in urothelium and detrusor muscle of the pig and human. We have hind that M2 muscarinic, receptor subtypes were predominantly present in both urothelium and detrusor of the pig bladder. However M3 muscarinic receptor subtypes were more hind in urothelium and smooth muscle of the human bladder Among β-receptor subtypes, β3-adrenoceptor were predominantly found in detrusor muscle of the pig and human.The expression of RhoA was more hind in the urothelium than in the smooth mule of the bladder in pig and human. The activity of RhoA determined by Western blotting were also greater in the urothelium than in the smooth muscle of the pig bladder.In functional studies, the responses to Y-27632 and fasudil, Rho-kinase inhibitors, were examined in bladder … More tissue strips with or without urothelium. Mansion decrease after administration of Y-27632 (InM-100μM) was significantly greater in tissues with intact urothelium than in tissues without urothelium, after pre-contraction with KCl (decrease by 52.0±4.6% vs 28±6.8%, respectively; p=0.0088) or with carbachol (decrease by 53.1±7.2% vs 30.6±5.81%, respectively; p=0.0035). Maximum contraction on CRC to carbachol was reduced significantly alter administration of 3, 10 and 30μM Y-27632 (to 72.2±6.8%, 43.9±7.1%, and 25.015.5%, respectively of the control value) in strips with intact urothelium (n=36), but was reduced only at 10 and 30 μM (to 66.7±825% and 85.6±2.6%, respectively) in tissues without urothelium Inhibitory effect of Y-27632 (3- 30μM) on the response to electrical field stimulation at 20Hz and 50 Hz was also greater in tissue strips with intact urothelium than in tissues without urothelium.In conclusion, the expression of RhoA mRNA and activated RhoA were greater in urothelium than in bladder smooth muscle. Y-27632 showed a stronger inhibitory effect on tissue preparations with intact urothelium than co those without urothelium. Less