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

We investigated mesonephric tubular-derived efferent ductules in female wild-type (WT) and estrogen receptor-α knockout (ERαKO) mice from late fetal to adult life. On gestational day 17, efferent ductules in both fetal WT and ERαKO 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 ERαKO females. By day 23, however, marked phenotypic differences occurred in efferent ductules of WT and ERβKO vs. ERαKO female mice. In the latter, efferent ductules became hypertrophied and dilated, whereas only small tubules remained in WT and ERβKO adult mice. The serum testosterone concentrations were similar in 21- to 25-day-old ERαKO, heterozygous, and WT female mice, suggesting that increased testosterone was not inducing enlargement of efferent ductules in ERαKO 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 ERαKO female mice. The underlying mechanism inducing hypertrophy and dilation of efferent ductules in ERαKO females is not clear, but secretory and/or reabsorptive function of female efferent ductules may involve ERα.