Urodynamic effects of estradiol (E2) in ovariectomized (ovx) rats

Whether estrogens have a beneficial effect in the urinary bladder to prevent or to delay occurrence of urinary bladder incontinence is an open question. Good animal models are missing. Therefore, in ovariectomized (ovx) rats we studied the effects of estradiol (E2) administered with food for 3 mo on urodynamic properties of the urinary bladder and the urethra. A biluminal catheter with one outlet in the bladder and another in the urethra in juxtaposition to the external sphincter was inserted in isoflurane anaesthetized animals. Within 2 x 30 s (1 min apart) 0.5 mL Ringer's solution was infused into the bladder and the inner vesicular and urethral pressure were recorded. In comparison to ovx estradiol-treated rats, ovx animals had significantly (p < 0.05) lower vesicular and urethral pressure. In the sham-treated ovx animals vesicular and urethral pressures were unstable and appeared uncoordinated, whereas estrogens increased vesicular and urethral pressure in a coordinated way, such that in these animals leaked volume was significantly lower than in the sham-treated ovx animals. By means of quantitative RT-PCR we demonstrate that the upper and lower part of the bladder and the urethra express estrogen receptor of the alpha- and beta-subtype (ER alpha and beta) and nerve growth factor, which is associated with painful sensations in inflamed urinary bladders. E2 downregulated both ERs in the bladder but not in the urethra, while NGF gene expression was downregulated in the urethra but unaffected by E2 in the bladder. It is concluded that estrogen deprivation causes uncoordinated function of the detrusor and sphincter muscles and that this effect can be prevented by estradiol.