Comparison of urodynamic effects of phytoestrogens equol, puerarin and genistein with these of estradiol 17β in ovariectomized rats

Whether urinary incontinence in the postmenopause can be prevented or delayed by estrogens is currently controversially debated. Ovariectomized (ovx) rats have been successfully used as models in the past years but plant derived substances with estrogenic effects in the lower urinary tract have not been studied so far. Therefore we compared the effects of a 3 months lasting oral administration of estradiol 17β (E2) with those of the phytoestrogens equol, genistein and puerarin. They were ovariectomized, fed with test substance containing food and then anaesthetized and catheterized with a biluminal catheter having one outlet in the bladder and another in the urethra at the level of the urethral sphincter. Urethral and bladder pressure were recorded during a 240 s period of retrograde bladder filling (2 × 0.5 ml within 30 s with 1 min filling intermission).Bladder and urethra pressures were highest in the E2 > puerarin > equol > genistein treated animals. Phytoestrogen and E2 treatment resulted in consistently higher urethral than the bladder pressures during the filling period and in the filled status whereas bladder often exceeded urethral pressures in ovx controls. In summary, we demonstrate significant improvement of urethral closure mechanism under E2 and phytoestrogen administration that can be assumed to be beneficial for prevention or therapy of postmenopausal urge incontinence.