Abstract
Gonadotropin-releasing hormone (GnRH) is a key factor at the onset of puberty. This decapeptide has been found in mammalian ovaries, but its regulatory mechanism in the ovary of sheep at the onset of puberty is not clear. This study investigated the coding sequence (CDS) of the GnRH gene in the ovary of Duolang sheep and the expression of GnRH mRNA in different tissues at the onset of puberty, and analyzed the effect of GnRH on ovarian granulosa cells (GCs) of Duolang sheep. The results showed that the GnRH CDS of sheep was cloned, the full length of the GnRH CDS in sheep ovary was 279 bp, and the nucleotide sequence was completely homologous to that in the hypothalamus. The expression of GnRH mRNA was highest in the hypothalamus and ovary. The expression of related hormones and receptors in GCs of Duolang sheep treated with different concentrations of GnRH for 24 h was affected. GnRH significantly inhibited LH synthesis and LHR expression in GCs. Low concentration (100 ng mL −1-1<math><msup><mi></mi> <mrow><mo>-</mo> <mn>1</mn></mrow> </msup> </math> ) had the most obvious therapeutic effect on follicle-stimulating hormone (FSH) and FSHR. Higher concentration (250 ng mL −1-1<math><msup><mi></mi> <mrow><mo>-</mo> <mn>1</mn></mrow> </msup> </math> ) significantly promoted estradiol and ER ββ<math><mi>β</mi></math> mRNA. These findings provide strong evidence that ovarian GnRH is an important regulatory factor at the onset of puberty in sheep.