Effects of Estrogen on Detrusor Contractillity of Bladder in Rats with Immune-induced Cystitis

Abstract

Purpose: We have used the sensitized rat model to study the effects of ovariectomy and estradiol replacement on contractile response of bladder muscle strips. Materials and Methods: Sprague-Dawley rats were ovariectomized or sham operated, treated with oil β-estradiol, and sensitized by intraperitoneal injection of ovalbumin. The experiments were performed 3 weeks after last injection. Sensitized rats were treated with intravesical ovalbumin (antigen challenge) and controls with normal saline. The bladders were removed for the bladder muscle strip studies and measuring mast cell density in the submucosa and detrusor muscle layer. Results: In the control group, overiectomy caused decreases in contractile responsiveness to bethanechol, but increases in contractile responsiveness to field stimulation. Estradiol treatment had no effect on responsiveness to bethanechol, but decreased contractile responsiveness to field stimulation. In the sensitized group, ovariectomy caused increased responsiveness to bethanechol, but had no effect on responsiveness to field stimulation. The contractile responsiveness to bethanechol was lower in both sham operated and ovariectomized rats of the sensitized group than in those of the control group. The contractile reponsiveness to field stimulation was higher in sham operated rats of the sensitized group than in those of the control group. There was no statistical difference in submucosal mast cell densities among the groups. There was a significant difference in detrusor mast cell density in the control groups treated with estradiol. In the sensitized group, there was a slight increase in detrusor mast cell density compared to the control group. Conclusions: We were able to successfully induce cystitis in rats by immunologic methods that depended on an allergic response to the bladder mucosa. This experimental cystitis expressed histologic features similar to interstitial cystitis of humans. The ovariectomy and estradiol treatment affected contractile responsiveness of bladder muscle strips to bethanechol and field stimulation. Our results suggest that ovariectomy and estradiol treatment may affect sensitization to ovalbumin but further studies are required.