Effect of Estrogen Replacement Therapy on Bladder Circulation in Old Female Rats

The effect of estradiol (E2) on the urinary bladder of old female rats was investigated by examining the histology and blood flow in the bladders. A total of 20 female Wistar rats aged 16 months were divided into 4 groups: Group I, 5 normal controls; Group II, 5 rats treated with E2 for 4 weeks; Group III, rats treated with E2 for 8 weeks; and Group IV, 5 rats receiving a placebo for 8 weeks. After the treatment, we removed the bladders, then weighed and stained them with hematoxylin and eosin. The muscle content was analyzed with the Elastica-van Gieson method, and the number of blood vessels with the Masson's trichrome method. Blood circulation in the bladders was also measured. The E2-replaced groups showed higher levels than the other groups in terms of blood flow in the bladder (20.6 ± 1.8 mL/min for Group II and 23.4 ± 1.5 mL/min for Group III, both P < 0.05 versus Groups I and IV), muscle content (2.33 ± 0.47 and 3.11 ± 0.48 for Groups II and III, respectively, both P < 0.05 versus Groups I and IV) and bladder weight (185.3 ± 6.2 mg and 193.2 ± 23.5 mg for Groups II and III; Group III showed P < 0.05 versus Groups I and IV). Differences in body weight and number of blood vessels among groups were not significant. We observed an increase in blood circulation, muscle content and weight of the bladder: E2-replacement therapy positively affected bladder functions.