The Effect of Ischemia/Reperfusion on Rabbit Bladder—Role of Rho-kinase and Smooth Muscle Regulatory Proteins

Objectives To detect the effect of ischemia/reperfusion (I/R) injury on rabbit bladder, using physiological study and immunoblotting techniques. Methods Twelve male New Zealand White rabbits were separated into three groups of 4 rabbits each. Group 1 served as control. Group 2 rabbits (ischemia-alone group) underwent in vitro bilateral ischemia surgery for 2 hours. In group 3 (I/R group), bilateral ischemia was similarly induced, and the rabbits were allowed to recover for 2 weeks. The contractile responses to electrical field stimulation, adenosine triphosphate, carbachol, and KCl were recorded. Expression levels of the signaling targets, Rho-kinase (ROK), protein kinase C potentiated inhibitor (CPI-17), caldesmon (CaD), and calponin (CaP) were analyzed by Western blotting. Results Ischemia alone resulted in significant reductions in the contractile responses, whereas I/R resulted in further decreases after all forms of stimulation. In muscle layer, ROK expression increased immediately after ischemia and recovered to the control level after 2 weeks' recovery. However, in mucosa layer, ROK expression showed no significant change after ischemia but significantly increased after reperfusion. After ischemic damage, CPI-17, the functional protein involved in smooth-muscle Ca2+ sensitization, was significantly increased and then decreased after 2 weeks of reperfusion. The expression of CaP significantly increased after ischemia and decreased after reperfusion. Levels of high-molecular-weight CaD significantly decreased after ischemia and remained very low after reperfusion. Conclusions This study provides further understanding of the role of regulatory proteins in detrusor muscle after ischemia and I/R-induced contractile dysfunction.