Effects of prolonged vaginal distension and β-aminopropionitrile on urinary continence and urethral structure

Objective: To investigate the effects of prolonged vaginal distension and β-aminopropionitrile (BAPN) on the urinary patterns and urethral structure in female virgin rats.

Methods: A total of 21 female virgin rats were randomly divided into 3 groups of 7 rats each. The control group received no intervention; the vaginal distension (VD) group was treated with prolonged VD by balloon inflation; and the VD plus BAPN group was treated with VD plus intraperitoneal injection of 150 mg/kg of BAPN every 3 days. Three weeks later, all the rats underwent conscious cystometric analysis and were then killed for histologic analysis of the urethra.

Results: Conscious cystometry identified 0, 3, and 5 rats in the control, VD, and VD plus BAPN groups with an abnormal voiding pattern, respectively. The urethral collagen content was significantly lower in the VD and VD plus BAPN rats compared with the control rats. The urethral elastic fibers were disorganized and shorter in the VD and VD plus BAPN rats and were fragmented and lacking the intermuscle connections in the VD plus BAPN rats. The urethral striated muscle fibers were shorter and more widely spaced in the VD and VD plus BAPN rats than in the control rats. Additionally, those in the VD plus BAPN group exhibited an abnormal wavy shape suggestive of a lack of architectural support.

Conclusion: Prolonged vaginal distension caused urodynamic changes and histologic abnormalities in the urethra, including reduced collagen content, fragmented elastic fibers, and sparsely arranged and shortened striated muscle fibers. BAPN appears to interfere with the restoration of collagen and elastic fibers.