THE EXPRESSION OF THREE GONADOTROPIN SUBUNITS IN RESPONSE TO 17-ETHYNYLESTRADIOL IN MALE PELTEOBAGRUS FULVIDRACO

In this paper, we investigated how 17-Ethynylestradiol(EE2) regulated the expression of three gonadotropin subunits in male Pelteobagrus fulvidraco. We cloned the full-length cDNA sequences of two subunits of gonadotropin hormone(FSH and LH) from the pituitary of Pelteobagrus fulvidraco by using RACE. We explored the tissue-specific and the seasonal pattern of expression of the genes. Male Pelteobagrus fulvidraco(2 years old) were exposed to EE2(100 ng/L) for 28 days. We found that the length of FSH cDNA sequence was 528 bp and it contained a 399-bp open reading frame(ORF) which encoded a precursor protein of 132 amino acids(aa). The length of LH cDNA sequence was 870 bp and it contained a 417 bp ORF that encoded a precursor protein of 138 aa. The sequence analysis showed that FSH had a predicted signal peptide of 17 aa, 2 N-glycosylation sites, and 13 cysteine residues. LH had a predicted signal peptide of 18 aa, 1 N-glycosylation site, and 12 cysteine residues. The phylogenetic analysis showed that FSH and LH were closely related to other Siluriformes species. The tissue expression analysis suggested that all the gonadotropin subunits were expressed specifically in pituitary. The seasonal pattern of expression in both genders was that GtH and LH mRNA peaked in May and then decreased gradually, and the expression of FSH in female also peaked in May but the expression in male remained unchanged. We applied semi-quantitative RT-PCR and demonstrated that the expression of the three gonadotropin subunits was dramatically suppressed by EE2. We speculated that EE2 might reduce the generation of FSH and LH in the pituitary of male Pelteobagrus fulvidraco, which would probably inhibit spermatogenesis and the maturation of sperm and spermiation, and consequently impair the testicular development and reproduction.