The effect of ovariectomy and long-term estrogen replacement on bladder structure and function in the rat.
PURPOSE The use of estrogen replacement therapy for treating postmenopausal urinary incontinence is a controversial topic. We examined the behavioral, cystometric and histological changes that occur with long-term estrogen depletion and supplementation in rat bladders to determine the role of menopause in lower urinary tract dysfunction. MATERIALS AND METHODS A total of 40 female Sprague-Dawley rats were placed into 1 of 3 groups, including bilateral ovariectomy, bilateral ovariectomy plus estrogen replacement and control. The estrogen replaced group received a 0.25 mg. 16-week sustained release pellet (Innovative Research of America, Sanasota, Florida) placed subcutaneously. After surgery voiding frequency and volume were measured in 24-hour periods by placing animals in metabolic cages. After 16 weeks the rats underwent catheterization and continuous cystometry. The bladder was then removed and stained with Gomori trichrome. The collagen-to-smooth muscle density ratio was calculated for each specimen using current imaging software. RESULTS There was no significant difference in voiding patterns in the 3 groups, as measured by volume and voiding frequency. Cystometric data showed a trend toward higher voiding pressure, threshold pressure, baseline pressure and mean inter-voiding pressure in the ovariectomy group compared with the estrogen and control groups, although there was no statistical significance. Histological studies showed a higher mean collagen-to-smooth muscle ratio plus or minus standard deviation in the ovariectomy group (0.807 +/- 0.204) than in the ovariectomy plus estrogen replacement (0.709 +/- 0.118) and control (0.700 +/- 0.129) groups (p <0.05). Furthermore, when histological and cystometric data were compared for individual samples, we found a direct correlation of mean inter-voiding pressure (a measure of bladder instability) with the collagen-to-smooth muscle ratio (p <0.05). CONCLUSIONS Long-term estrogen replacement is beneficial for treating postmenopausal urinary incontinence.
Division of Urologic Research, Albert Einstein College of Medicine, The Bronx, New York, USA.
Nicole
N
Fleischmann
George
G
Christ
Theresa
T
Sclafani
Arnold
A
Melman
D000818:Animals; D003238:Connective Tissue / Q000033:anatomy & histology / Q000737:chemistry; D015914:Estrogen Replacement Therapy; D004967:Estrogens / Q000502:physiology; D005260:Female; D009130:Muscle, Smooth / Q000166:cytology; D010052:Ovariectomy; D051381:Rats; D017207:Rats, Sprague-Dawley; D001743:Urinary Bladder / Q000166:cytology / Q000187:drug effects / Q000502:physiology*; D014563:Urodynamics
D004967:Estrogens