The expression of pituitary FSHbeta and LHbeta mRNA and gonadal FSH and LH receptor mRNA in the chicken embryo.

In avian species, synthesis of sex steroids by embryonic gonads is regulated by luteinizing hormone (LH) and follicle-stimulating hormone (FSH). In order to elucidate the role of the two gonadotropins in gonadal axis development during the second half of chicken embryogenesis, pituitary expression of LH beta subunit (LHbeta) and FSH beta subunit (FSHbeta) mRNAs as well as gonadal expression of LH and FSH receptor (LHR and FSHR) mRNAs were determined on days 11 (E11) and 17 (E17) of embryonic development and after hatching (D1). In the pituitary of the female embryo, the gene expression of FSHbeta was the lowest on E11 and increased on E17. In the male pituitary, the expression of FSHbeta did not differ among the studied days. The FSHbeta mRNA expression on E11 was higher in the male than in the female pituitary gland. The expression of LHbeta mRNA in the female pituitary increased on D1 in comparison to E11. In the male pituitary gland, the expression of LHbeta gene was relatively constant. The expression of mRNA encoding FSHR in the ovary increased on E17, while in testes it did not differ among the studied days. There were no significant alterations in LHR gene expression in the ovary or in the testes in the examined period however, the gene expression on E17 was higher in the ovary than in the testes. We observed positive correlations between the pituitary FSHbeta mRNA expression and ovarian expression of FSHR mRNA (r = 0.63; p<0.01) as well as between LHbeta mRNA and LHR mRNA in the testes (r=0.65; p<0.01). The reported alterations in gene expression of FSHbeta, LHbeta and their receptors between sexes and among the stages of embryonic development indicate time- and sex-dependent action of gonadotropins in gonads of chicken embryos.