Insensitivity of the chick embryo Müllerian duct to human recombinant Müllerian-inhibiting substance

: To determine whether mammalian Mullerian-inhibiting substance (MIS) is active in birds, Mullerian ducts from 7- to 8-day-old male or female chick embryos were cultured in the presence of human recombinant MIS at concentrations between 2.5 and 12.5 micrograms/ml. None of 20 ducts regressed at any concentration. In contrast, at concentrations of 2.5-5 micrograms/ml, all 12 Mullerian ducts from 13-day-old male mouse embryos and 13 out of 14 female ducts were inhibited to varying degrees. It is concluded that avian Mullerian ducts are unresponsive to mammalian MIS. There may be a difference in structure between the MIS of birds and mammals, or the signal-transduction system may be different.