[Effect of ovariectomy and estrogen replacement on bladder function and structure in rats].
OBJECTIVE
To investigate the mechanism of estrogen action on bladder.


METHODS
By examining the functional, histological and ultrastructural changes that occurred in the bladder of rats with estrogen depletion and supplementation, we studied the actions of estrogen on bladder. A total of 30 female adult Sprague-Dawley rats were divided into 3 groups, including control group, bilateral ovariectomy (OVX) group and bilateral ovariectomy plus estradiol valerate (OVX + E) group. After medication for 12 weeks, cystometry was performed. Masson stain was used to quantify the area densities of collagen fiber and smooth muscle and their ratios, and electron microscopy was used to evaluate ultrastructure of detrusor muscle.


RESULTS
In OVX group, bladder maximal capacity, (0.32 +/- 0.20) ml, compliance, (0.012 +/- 0.006) ml/cm H2O (1 cm H2O = 0.098 kPa), and maximal contraction force, (1.4 +/- 0.4) cm H2O were obviously lower than those in control group, which were (1.11 +/- 0.09) ml, (0.026 +/- 0.003) ml/cm H2O, and (4.4 +/- 0.3) cm H2O, respectively (P < 0.05). In OVX + E group, bladder maximal capacity (0.83 +/- 0.10) ml was lower than that in control group (P < 0.05), but compliance, (0.029 +/- 0.003) ml/cm H2O and maximal contraction force, (4.8 +/- 1.4) cm H2O were similar to those of control group (P > 0.05). Collagen fiber area density and collagen fiber to smooth muscle area density ratio in OVX group (0.218 +/- 0.041 and 0.54 +/- 0.08) were higher than those in control group (0.160 +/- 0.039 and 0.32 +/- 0.09, P < 0.05); however, there were no significant differences between OVX + E group (0.178 +/- 0.027, 038 +/- 0.06) and control group (P > 0.05). In OVX group, ultrastructure of detrusor muscle showed degenerative change, while it was not found in the other groups.


CONCLUSIONS
When the rat was ovariectomized, bladder function became poor and supplementary estrogen could improve bladder function. This effect may be due to inhibition of collagen hyperplasia and protection of cell organelles. Estrogen replacement should be beneficial for treating postmenopausal lower urinary tract symptoms.
Li
Ya-Zhen
YZ
Department of Obstetrics and Gynecology, First Hospital, Peking University, Beijing 100034, China.
Yang
Xin
X
Wu
Shi-Liang
SL
Shang
Min
M
Wu
Qiong
Q
Liao
Qin-Ping
QP
D000818:Animals; D004958:Estradiol / Q000494:pharmacology*; D015914:Estrogen Replacement Therapy; D005260:Female; D009119:Muscle Contraction / Q000187:drug effects / Q000502:physiology; D018485:Muscle Fibers, Skeletal / Q000187:drug effects / Q000502:physiology; D009130:Muscle, Smooth / Q000187:drug effects / Q000502:physiology / Q000648:ultrastructure; D009929:Organ Size / Q000187:drug effects; D010052:Ovariectomy; D051381:Rats; D017207:Rats, Sprague-Dawley; D001743:Urinary Bladder / Q000187:drug effects / Q000502:physiology*; D014563:Urodynamics
D004958:Estradiol