Purpose: Our previous report showed aging caused bladder dysfunction in spontaneously hypertensive rats (SHRs). In this study, we investigated the protective effects of an antihypertensive drug, angiotensin II type 1 receptor blocker losartan on bladder dysfunction in aged SHRs.
Materials and Methods: Thirty-six-week-old male SHRs were orally treated with losartan (0, 3 or 10 mg/kg) once daily for 18 weeks. Vehicle-treated Wistar Kyoto rats (WKYs) were used as normotensive controls.
Results: Vehicle-treated SHRs had significantly higher detrusor thickness, bladder arterial wall thickness compared to vehicle-treated WKYs. Moreover, SHRs showed significantly higher single voided volume (SVV), post-voiding residual urine volume (RV), bladder capacity (BC), and intercontraction interval (ICI) and lower voiding efficiency compared to vehicle-treated WKYs. A low dose of losartan decreased RV, BC and ICI but not mean blood pressure in SHRs. A high dose of losartan ameliorated changes in mean blood pressure, detrusor thickness, bladder arterial wall thickness, SVV, RV, BC and ICI in SHRs.  
Conclusion: Treatment with losartan ameliorated bladder dysfunction in aged SHRs.