[Precocious production of müllerian inhibitor by the fetal rabbit testis]

The production of müllerian inhibitor (or anti-müllerian hormone) by the testes of the Rabbit fetus was studied in vitro by co-culturing them with castrated genital tracts from 14.5 day old female Rat fetuses for three days. Under these conditions testes from 14 day old Rabbit fetuses were inactive. The testes from 15, 16 and 17 day old fetuses in which seminiferous cords are forming, had anti-müllerian activity, the older the stronger. In vivo this activity does not prevent the Müllerian ducts from growing in male Rabbits as well as in females until near to day 20; in vitro the fetal Rat ducts also grew in length despite the testicular anti-müllerian activity.