Testosterone and dihydrotestosterone in sexual ducts and genital tubercle of rabbit fetuses during sexual organogenesis: effects of fetal decapitation.

Testosterone (T) and dihydrotestosterone (DHT) have been measured in the plasma, sexual ducts and genital tubercle in rabbit fetuses of both sexes during sexual organogenesis. T and DHT were also measured in decapitated male fetuses. In male, T appeared successively in testes (day 19), mesonephros (day 20) and Wolffian ducts (day 22). In sexual ducts, T levels increased from 20 to 25 days, then stabilized until birth. Since DHT was measurable, in sexual ducts of males only from 24 days onwards, T itself is the active hormone on the differentiation of Wolffian ducts. In female fetuses, T and DHT were undetectable, in sexual ducts, at any gestational age. In the genital tubercle T was undetectable in both sexes. In the genital tubercle of males DHT levels increased from 19 to 25 days, then stabilized. In female fetuses, DHT was episodically measurable in the genital tubercle but at levels always lower than in males. DHT is the active hormone on the differentiation of genital tubercle. In male decapitated fetuses T and DHT levels were reduced in sexual ducts and genital tubercle but the differences were not significant.