Testicular inhibition of fetal Mullerian ducts in vitro: effect of dibutyryl cyclic AMP.

The effect of dibutyryl cyclic AMP (dibutyryl cAMP) on Mullerian ducts of 141/2-day-old rat fetuses in vitro was investigated. Dibutyryl cAMP was unable to produce the typical regression of Müllerian ducts which is observed in vivo in male fetuses and in vitro with Müllerian ducts in the presence of testes. Effects of dibutyryl cAMP and theophylline on regeneration of Müllerian ducts induced by fetal testes were also investigated, and it was found that 10(-3) dibutyryl cAMP added to the culture medium prevented the normal regression. Lower concentrations and theophyline (10(-3)M) were ineffective. An effect of lower doses of dibutyryl cAMP was obtained only when theophylline was also present. Because pretreatment of testes with dibutyryl cAMP did not prevent the inhibiting action of testes on Müllerian ducts, it is concluded that an interaction between dibutyryl cAMP and the inhibiting factor at the level of the target organs must be considered.