Female Urethra: A Target for Estrogen Action

It is not uncommon to use estrogen therapy in patients with urinary stress incontinence. The possibility of a selective action of estrogen in the lower urinary tract was examined. Wet weight of the uterus, vagina and urethra increased significantly, and that of the urinary bladder insignificantly after estradiol treatment of ovariectomized rabbits. When ovariectomized rabbits were injected i.v. with 3H-estradiol, the tritium concentration, determined after 1 hour, was 3 to 4 times higher in urethra, urinary bladder and vagina than that in the muscle. High affinity estradiol receptors (KD approximately 1 X 10(-9) M) could be demonstrated in both the cytoplasmic and nuclear fractions prepared from the female rabbit urethra and bladder. The concentrations of estradiol receptors in the urethra and bladder were about 10 and 20 times lower respectively than those in the uterus. The present evidence for estradiol receptors in the lower urinary tract supports the case for estradiol therapy in urinary incontinence.