[Period of sensitivity to androgens of the Wolff duct of the rat fetus].

The external and internal (lumen) diameter and the height of the epithelium of the Wolffian ducts of control rat fetuses were measured between 14 days 8 hrs and 21 days 8 hrs at the level of the gonad and in the genital folds. In males, at the level of the gonad, these ducts display a transitory increase in diameter and lumen at 16 days 8 hrs of fetal age. This increase, which is absent in females, occurs just before the development of the epididymides and might reflect the endocrine activity of the fetal testis. In the females, the first involutive changes appear at both levels at 17 days 8 hrs of age (decrease in diameter by reduction of the lumen and height of the epithelium). After injections of androgens to pregnant rats or directly into the fetuses in utero, the Wolffian ducts can be maintained in female fetuses only if submitted to androgens before and until 16 days 16 hrs. If the treatment starts once the involutive changes have appeared (17 days 8 hrs) inconstant persistence is obtained. The portions of ducts still present on day 18 cannot be maintained by androgens any more. Even if injected at 15 days 8 hrs, exogenous androgens do not hasten or anticipate the formation of Wolfian derivatives (epididymides and seminal vesicles) in males or in females.