title: Hypothalamus-pituitary-gonad axis of rainbow trout (Oncorhynchus mykiss) during early ovarian development and under dense rearing condition.
abstract: 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.
authors.affiliation: Fisheries College, Ocean University of China, Qingdao 266003, China.
authors.forename: Zhi-Shuai
authors.initials: ZS
authors.lastname: Hou
authors.affiliation: Fisheries College, Ocean University of China, Qingdao 266003, China. Electronic address: wenhaishen@ouc.edu.cn.
authors.forename: Hai-Shen
authors.initials: HS
authors.lastname: Wen
authors.affiliation: Fisheries College, Ocean University of China, Qingdao 266003, China.
authors.forename: Ji-Fang
authors.initials: JF
authors.lastname: Li
authors.affiliation: Fisheries College, Ocean University of China, Qingdao 266003, China.
authors.forename: Feng
authors.initials: F
authors.lastname: He
authors.affiliation: Fisheries College, Ocean University of China, Qingdao 266003, China.
authors.forename: Yun
authors.initials: Y
authors.lastname: Li
authors.affiliation: Department of Anatomy, Physiology and Pharmacology, College of Veterinary Medicine, Auburn University, Auburn, AL 36849, United States.
authors.forename: Ya-Xiong
authors.initials: YX
authors.lastname: Tao
mesh_terms: D000818:Animals; D005260:Female; D012739:Gonadal Steroid Hormones / Q000378:metabolism*; D006065:Gonadotropins, Pituitary / Q000378:metabolism*; D007031:Hypothalamus / Q000378:metabolism*; D017686:Oncorhynchus mykiss / Q000235:genetics* / Q000254:growth & development / Q000378:metabolism*; D010053:Ovary / Q000378:metabolism*
chemical_list: D012739:Gonadal Steroid Hormones; D006065:Gonadotropins, Pituitary
keywords: Density; Ovarian development; Rainbow trout; Steroid hormone; fsh/lh; gnrh