The differential fate of mesonephric tubular-derived efferent ductules in estrogen receptor-alpha knockout versus wild-type female mice.

We investigated mesonephric tubular-derived efferent ductules in female wild-type (WT) and estrogen receptor-alpha knockout (ERalphaKO) mice from late fetal to adult life. On gestational day 17, efferent ductules in both fetal WT and ERalphaKO females were well developed and morphologically similar, although one third the size of the male counterpart. Unexpectedly, efferent ductules with a ciliated epithelium were still present on postnatal day 10 in WT and ERalphaKO females. By day 23, however, marked phenotypic differences occurred in efferent ductules of WT and ERbetaKO vs. ERalphaKO female mice. In the latter, efferent ductules became hypertrophied and dilated, whereas only small tubules remained in WT and ERbetaKO adult mice. The serum testosterone concentrations were similar in 21- to 25-day-old ERalphaKO, heterozygous, and WT female mice, suggesting that increased testosterone was not inducing enlargement of efferent ductules in ERalphaKO females. In conclusion, remnants of efferent ductules persisted in normal adult female mice, although these structures were greatly reduced in size compared with efferent ductules in ERalphaKO female mice. The underlying mechanism inducing hypertrophy and dilation of efferent ductules in ERalphaKO females is not clear, but secretory and/or reabsorptive function of female efferent ductules may involve ERalpha.