Altered expression of caveolin 2 and 3 in smooth muscle of rat urinary bladder by 17β-estradiol

BACKGROUND The purpose of this study was to investigate the effect of estrogen alteration on the expression of caveolin 2 and 3 in rat smooth muscle of urinary bladder. METHODS Female Sprague-Dawley rats were divided into three groups: control, bilateral ovariectomy (Ovx), and bilateral ovariectomy followed by subcutaneous injections of 17β-estradiol (Ovx+Est). After 4 weeks, urodynamic measurements were taken to ascertain the contraction interval and contraction pressure. The expression and cellular localization of caveolin 2 and 3 were determined by Western blot and immunohistochemistry in rat urinary bladder smooth muscle. RESULTS In cystometrograms, the contraction interval (min) was significantly lower in the Ovx group (3.1±1.5) than in the control group (5.6±1.2), but was increased after estrogen treatment (9.3±1.0). Conversely, the average contraction pressure (mmHg) was higher in the Ovx group (26.2±2.3) than in the control group (21.9±3.1), and was decreased after estrogen treatment (23.8±3.5). Caveolin 2 and 3 expression was localized in the cell membrane of the smooth muscle. The protein expression of both caveolin 2 and 3 was significantly lower after ovariectomy and was restored to the control levels after 17β-estradiol treatment. CONCLUSIONS Hormonal alteration causes a significant change in the expression of caveolin 2 and 3 in smooth muscle of rat urinary bladder. These findings suggest that these molecules might have functional roles in the detrusor overactivity that occurs in association with hormonal alteration.