The Dome Wall of Bladder Acts as a Pacemaker Site in Detrusor Instability in Rats

BACKGROUND The aim of this study was to confirm that the interstitial cells of Cajal (ICCs) in the dome wall of the bladder are pacemaker cells, and that the dome wall of the bladder acts as a pacemaker site in the detrusor instability (DI) rat model. MATERIAL AND METHODS The model of DI in Wistar rats was established and urodynamic studies measuring the bladder volume and pressure were performed. The detrusor excitability was investigated using the amplitude and frequency of phasic contraction of strips. The localization and quantity of ICCs was identified by immunohistochemistry and c-KIT protein expression in the rat bladder. PCR assay and Western blot were used to assess the expression of HCN2 and Cx43. RESULTS The bladder capacity, residual volume, voiding volume, and maximum voiding pressure were significantly increased in the DI group. The contraction frequency and amplitude of the strips from the dome of the bladder in the DI group were higher than the triangle, body, and base parts. Both the concentration of c-KIT positive ICCs cells and expression of the c-KIT protein in the dome wall were higher than in other parts of the bladder. The expression of HCN2 and Cx43 in each part of the DI rat group were obviously higher than each part in the control group. Compared to the body, base, and triangle parts, the expression of HCN2 and Cx43 in the dome wall were obviously higher in the DI group. CONCLUSIONS The quantity of ICCs was higher in the dome wall and the dome wall of bladder acts as a pacemaker site in the DI rat model.