Expression of androgen receptors in upper human fetal reproductive tract

BACKGROUND: Androgens play a key role in human fetal development. All androgens act through a single intra-cellular androgen receptor (AR), which is encoded by a single copy gene on the X chromosome. ARs are expressed as early as 9 weeks in the epithelium and mesenchyme of the urogenital sinus, paramesonephric (MuÈllerian) and mesonephric (Wolf®an) ducts. METHODS: Using immunohistochemistry, we investigated the distribution of ARs in the gonads and lower genital tracts of 54 human fetuses at 8±11 weeks of gestation. Gender was determined by PCR. RESULTS: The AR was expressed in a similar pattern in both male and female fetuses. There appears to be no difference in expression in the mesonephros or the mesonephric ducts when male and female pelvises were com-pared. Expression in the female paramesonephric duct was within the epithelium, whereas, in the male pelvises, expression was in the mesenchyme of the paramesonephric duct. When AR expression was compared in the ovary and testes, both gonads seem to express AR at 9 weeks, but this expression was extended into the 10th week of gesta-tion in the male. CONCLUSION: The speci®c pattern of AR expression implies a key role in gonadal development. However, the pattern of staining was similar in the gonads at 8 and 9 weeks in both sexes, although staining persisted longer in the testis until the 10th week. AR expression, therefore, is not a key determinant of human gonadal differentiation. Key words: androgen receptor/fetus/gonad/immunohistochemistry/mesonephro