Androgen receptors (AR) are highly expressed in female reproductive organs. In order to define the possible involvement of estrogens in the regulation of AR expression in the uterus and vagina, we have studied the effect of short-term administration of 17beta-estradiol (E2) to ovariectomized adult mice on AR mRNA levels. Seven days after ovariectomy, the mice received a single injection of E2 (0.05 microg/mouse) 3, 12 or 24 h before they were killed. The levels of AR mRNA were measured in the different uterine and vaginal compartments using quantitative in situ hybridization. In the uterus, AR mRNA was expressed in the luminal and glandular epithelial cells, stromal cells and smooth muscle cells. In the vagina, AR mRNA was localized in both epithelial and stromal cells. In the uterus after ovariectomy, AR mRNA levels were decreased by 18% in the epithelial cells, 23% in the stromal cells and 50% in the myometrial cells. AR mRNA levels were completely restored as early as 3 h after E2 administration in the epithelium and stroma, and at the 12-h time-interval in the myometrium. In the vaginal epithelium, ovariectomy induced a 70% decrease in AR mRNA expression. No effect could be detected 3 h after E2 administration, while at the longest time-intervals (12 and 24 h) there was an increase in mRNA levels corresponding to 70% of the levels observed in intact animals. In the vaginal stroma, ovariectomy was responsible for a 55% decrease in mRNA levels. While no significant changes were observed at the 3-h time-interval, a complete restoration of AR mRNA levels in stromal cells could be recorded at the longest time-intervals after E2 administration. The data obtained indicated that, in adult mice, estrogens exert a positive regulation of AR mRNA expression in the different compartments of both the uterus and the vagina.

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