Spontaneous inflammatory pelvic disease in adult non-castrated female rats treated with estrogen.

The adaptive immune response of the genital tract is under the control of sexual steroids; however, the influence of sex hormones on innate immune mechanisms of the genital mucosa are only beginning to be understood. We found that long-term estrogen treatment increases the risk for inflammatory pelvic diseases in adult non-castrated female rats. Female rats (110 g to 130 g) received estrogen (10 rats; 17-beta estradiol, 50 mg pellet; 10 rats: subcutaneous weekly injection of estradiol valerate 0.166 mg/kg). Ten rats received a pellet of 17-beta estradiol and were treated with amoxicillin, 50 mg/kg after the 90th day of exposure to estrogen. Three control groups of ten rats were also used. The estrogen-treated rats developed an inflammatory pelvic disease, with abscess formation after the third month of hormonal treatment. All the surviving animals were killed after six months of hormonal exposure. Among 15 survivors of the two groups that received estrogen 13 animals presented tuboovarian abscesses. Among eight survivors of the group treated with amoxicillin, six had tuboovarian abscesses. None of the 30 control rats presented macro or microscopic signs of inflammatory disease in the uterus, tubes or ovaries. We conclude that estrogen impairs the defense mechanisms of the genital tract of non-castrated female rats, enhancing bacterial growth in the vagina and ascending infection to the uterus, tubes and ovaries.