Evidence of sex reversal in the gonads of chicken embryos after oestrogen treatment as detected by expression of lutropin receptor.

In chicken embryos, there is a difference between the sexes in the onset of lutropin receptor mRNA expression in the gonads. The effects of oestrogen on lutropin receptor expression were studied to investigate the mechanism controlling this difference. Lutropin receptor mRNA expression was detected in the ovaries of sesame oil-treated control female embryos on day 12 of incubation, while no expression was found in the testes of the male controls. Oestradiol administration to genetically male embryos before sexual differentiation resulted in gonadal sex reversal which was characterized histologically by the proliferation of cortical cords and the presence of lacunae. Lutropin receptor expression was detected in the feminizing testis on day 12 of incubation. Administration of aromatase inhibitor (CGS 16949 A) to genetically female embryos before sexual differentiation inhibited the formation of cortical cords, although a relatively weak expression of lutropin receptor was detected. These results indicate that early expression of the lutropin receptor is regulated by oestrogen.