| Black rockfish (Sebastes schlegeli Hilgendorf) is considered as one of the most economic fishes in China Sea. In this study, we took black rockfish as the experiment fish and researched on ovary development, changes of steroid hormones, and organization expression pattern of three estrogen receptors by means of histological staining methods, radioimmunoassay and biochemical methods in details. The results we got are as follows:1. Histological study on ovary development in black rockfish.Black rockfish has a pair of ovary, which looks like two sac and the sizes are different. There is a thick mesoarium to fix ovary in situ and which connect genital duct at genital pore.The ovary development is considered to go through 7 typical development steps, and oocyte growth has 6 stages. The period from September to November is the time that primary oocytes grow up and egg yolk accumulates. Till up to April in the next year, oocytes develop mature which don't need vitellogenin any more. In May, black rockfish is pregnant. The fertilized egg cells grow in ovary, and are spawned in the middle of May or early of June.2. Study on the changes of plasma sex steroid hormone levels in black rockfish during the reproductive cycle.Radio immunoassay (RIA) is used to detect plasma testosterone, progesterone and 17β-Estradiol in both sexes of black rockfish. The results show that progesterone and 17β-Estradiol have the same variation trend during the reproductive cycle. Both of them in female serum reach to the highest level before pregnancy, and then dropp down apparently. The level of testosterone tends to rise during the ovary development and the highest level shows up when fish were pregnant. The levels of progesterone and 17β-Estradiol in male serum go up in the early spermatogenetic cycle and after spermiation, which have been speculated might play important part in spermatogenesis and recrudescence. The level of testosterone also increases in the early spermatogenetic cycle, which suggests it involves in spermatogenesis.3. Molecular cloning and expression analysis of estrogen receptor (ERs) in black rockfish.In this experiment, there estrogen receptors are isolated from ovary of black rockfish. The full-length cDNA of ERα, ERβ1, ERβ2 consist of 2972, 2451, 2338 base pairs [bp] respectively, including an open reading frame (ORF) encoding deduced proteins of 624, 561, 659 amino acid residues. Biological softwares are used to compare the brfERs sequences with that of other ERs and some structure identities are found in these ERs sequence. In this paper, the tissue distribution of ERs mRNA in black rockfish is examined using RT-PCR. BrfERαis present in most tissues of female black rockfish, being more abundant in ovary, liver, duodenum and fat, whereas it has a restricted distribution in male fish. The expression of brfERβ1 also shows wider in tissues of female than that of male. Except muscle, brfERβ1 is present in other tissues, but more deficient in gill. In male, brfERβ1 mRNA is strongly expressed in liver, moderate expressed in testes, and also detected in duodenum, caecus, head kidney, and kidney. In black rockfish, ERs mRNA expression pattern appear to be gonad developmental stage-dependent throughout the annual reproductive cycle, especially in male. |
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