Effects of Aromatase Inhibitor on Sex Differentiation and Levels of P45017αand P450aromMessenger Ribonucleic Acid of Gonads in Chicken Embryos

Sex reversed chicks (Gallus domesticus) hatched from eggs treated with aromatase inhibitor YM511

“…Experiments conducted to study the consequences of hormonal changes for subsequent sex differentiation in female avian embryos have demonstrated that in ovo injection of steroidal and non-steroidal aromatase inhibitors may result in more or less marked changes of phenotypic sex including the evolution of female gonads into testis-like structures (Abinawanto et al, 1996). From the present observations performed in chickens, we demonstrate that the injection of aromatase inhibitor YM511 (1 mg per egg) into the albumen prior to incubation may result in the transformation of genetic females into neo-males (development of testicle-like structures) expressing male secondary sex characteristics.…”

“…The production of oestrogens, along with the presence of oestrogen receptors during the early stages of embryo development (≤ 5.5 days of incubation in chickens) play a crucial role in the phenotypic sex differentiation of females. Previous studies in the chicken indicated that genetic females could be transformed into neo-males after in ovo injection of steroidal and non-steroidal aromatase inhibitors (Abinawanto et al, 1996). Based on data obtained following the injection of various types of aromatase inhibitors (Wartenberg et al, 1992;Dewil et al, 1998), evidence exists that the loss of aromatase function in female embryos between 7 and 14 days old leads to partial phenotypic sex reversal of adult females accompanied by the development of secondary male sex characteristics along with the occurrence of testes containing some spermatozoa (Abinawanto et al, 1997).…”

Temperature-Dependent Sex Determination in Vertebrates

“…CYP19/aromatase is the P450 enzyme responsible for converting androgens into estrogens. Inhibition of its activity results in the differentiation of a right testes and a left testis or ovotestis in ZW female chickens (Abinawanto et al 1996; Elbrecht and Smith 1992;Vaillant et al 2001). Hence, estrogen is critical for female gonad development.…”

Rowley Review

“…4a) Smith et al 1997;Nakabayashi et al 1998). The importance of oestrogen for female development can be demonstrated by administering a single dose of an aromatase enzyme inhibitor in ovo, which results in testis development and female-to-male sex reversal (Elbrecht and Smith 1992;Abinawanto et al 1996;Vaillant et al 2001). As shown in Fig.…”