The effect of low-dose estrogen therapy on ovariectomized female rabbit bladder

OBJECTIVES To determine whether low-dose estrogen supplementation is as effective as high-dose supplementation in increasing bladder contractile function and mediating bladder hypertrophy and angiogenesis. METHODS Sixteen New Zealand white female rabbits were separated into four groups of 4 rabbits each. Group I served as the control, and groups 2 to 4 underwent ovariectomy. The group 2 rabbits were studied 7 days after ovariectomy. The rabbits in groups 3 and 4 were medicated with 17-beta estradiol at a dose of 0.1 mg/kg/day and 1.0 mg/kg/day, respectively, for 7 days. At the end of the experiment each rabbit was anesthetized and the bladder removed for contractile, morphologic, and biochemical studies. RESULTS Low- and high-dose estrogen administration resulted in similarly significant increases in the contractile responses to field stimulation, adenosine triphosphate, and potassium chloride. Similarly, both doses of estrogen mediated significant hypertrophy of the smooth muscle and decrease in collagen, similar levels of angiogenesis, and similar increases of citrate synthase activity. CONCLUSIONS Low-dose estrogen produces similar physiologic, morphologic, and biochemical effects on the bladder as have been shown for high-dose estrogen.