Hou Zhi-Shuai, Wen Hai-Shen, Li Ji-Fang, He Feng, Li Yun, Tao Ya-Xiong
Fisheries College, Ocean University of China, Qingdao 266003, China.
Fisheries College, Ocean University of China, Qingdao 266003, China.
Gen Comp Endocrinol. 2016 Sep 15;236:131-138. doi: 10.1016/j.ygcen.2016.07.011. Epub 2016 Jul 9.
The objective of this study was to determine the hypothalamus-pituitary-gonad (HPG) axis of female rainbow trout (Oncorhynchus mykiss) during early ovarian development and under high rearing density. Trouts were sampled from 240 (ovarian stage II) to 540 (ovarian stage IV) days following hatching (DFH) as control group (Ctrl, 4.6-31.1kg/m(3)) to determine HPG axis during early ovarian development. Trouts from the same batch of fertilized eggs were reared in two higher densities during 240-540 DFH as stocking density 1 and 2 (SD1, 6.6-40.6kg/m(3); SD2, 8.6-49.3kg/m(3)) to elucidate effects of high density on reproductive parameters. Dopamine, E2 (estradiol), 17α,20β-P (17α,20β-dihydroxy4-pregnen-3-one) and P4 (progesterone) were evaluated by radioimmunoassay or ELISA. mRNA expression of hypothalamic gnrh-1, -2 (gonadotropin-releasing hormone-1, -2), pituitary gonadotropins (fsh/lh, follicle-stimulating hormone/luteinizing hormone) and their cognate receptors (fshr/lhr) in ovaries were examined by qRT-PCR. Our findings demonstrated mRNA expression of hypothalamic sgnrh-1, pituitary fsh and ovarian fshr increased in early ovarian development (360 DFH). Serum 17α,20β-P and pituitary lh mRNA expression first increased when trouts were in ovarian stage III (420 DFH). Ovaries were at different stages when reared in different densities. Long-term high density treatment (over 31.7kg/m(3)) resulted in decreased hypothalamic sgnrh-1, pituitary fsh, ovarian fshr, serum E2, and increased hypothalamus gnrh-2 and serum dopamine during vitellogenin synthesis, suggesting HPG of rainbow trout might be retarded under dense rearing condition.
本研究的目的是确定雌性虹鳟（Oncorhynchus mykiss）在卵巢早期发育期间以及高养殖密度条件下的下丘脑 - 垂体 - 性腺（HPG）轴。从孵化后240天（卵巢II期）至540天（卵巢IV期）的虹鳟中取样作为对照组（Ctrl，4.6 - 31.1kg/m³），以确定卵巢早期发育过程中的HPG轴。同一批受精卵孵化出的虹鳟在240 - 540天期间以两种更高的密度养殖，分别作为养殖密度1和2（SD1，6.6 - 40.6kg/m³；SD2，8.6 - 49.3kg/m³），以阐明高密度对生殖参数的影响。通过放射免疫分析或酶联免疫吸附测定法评估多巴胺、E2（雌二醇）、17α,20β - P（17α,20β - 二羟基 - 4 - 孕烯 - 3 - 酮）和P4（孕酮）。通过qRT - PCR检测下丘脑gnrh - 1、 - 2（促性腺激素释放激素 - 1、 - 2）、垂体促性腺激素（fsh/lh，促卵泡激素/促黄体生成素）及其在卵巢中的同源受体（fshr/lhr）的mRNA表达。我们的研究结果表明，下丘脑sgnrh - 1、垂体fsh和卵巢fshr的mRNA表达在卵巢早期发育（360天）时增加。当虹鳟处于卵巢III期（420天）时，血清17α,20β - P和垂体lh mRNA表达首先增加。在不同密度养殖时，卵巢处于不同阶段。长期高密度处理（超过31.7kg/m³）导致在卵黄蛋白原合成期间下丘脑sgnrh - 1、垂体fsh、卵巢fshr、血清E2降低，而下丘脑gnrh - 2和血清多巴胺增加，这表明在密集养殖条件下虹鳟的HPG轴可能受到抑制。
