Müllerian inhibiting substance is present in testes of dogs with persistent müllerian duct syndrome.

Breeding studies in a strain of miniature schnauzer dogs with Persistent Müllerian Duct Syndrome (PMDS) indicate this syndrome is inherited as an autosomal recessive trait, as it is in man. Testes of neonatal dogs affected with PMDS and normal male littermates were examined for Müllerian Inhibiting Substance (MIS) production by immunohistochemistry and bioassay. MIS immunoactivity was detected in Sertoli cells of normal and affected pups using an avidin-biotin complex-enhanced method. Rat embryonic Müllerian ducts regressed when cocultured with testis fragments of both normal and affected pups in a graded organ culture bioassay, demonstrating that the MIS produced was bioactive. These findings indicate that Müllerian duct persistence in affected dogs is not due to a mutation in the structural gene for MIS, but rather, by inference, to a failure of response to MIS at the receptor level.