Influence of plasma lipid changes in response to 17β-oestradiol stimulation on plasma growth hormone, somatostatin, and thyroid hormone levels in immature rainbow trout |
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| Authors: | F Mercure A C Holloway D R Tocher M A Sheridan G Van der Kraak JF Leatherland |
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| Institution: | Department of Biomedical Sciences, Ontario Veterinary College, University of Guelph, Guelph, ON N1G 2W1, Canada;Institute of Aquaculture, University of Stirling, Stirling FK9 4LA, Scotland;Department of Zoology, North Dakota State University, Fargo, ND 58105, U.S.A.;Department of Zoology, College of Biological Sciences, University of Guelph, Guelph, ON N1G 2W1, Canada |
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| Abstract: | Plasma total lipids were significantly higher in 17β-oestradiol(E2)-treated immature rainbow trout Oncorhynchus mykiss at week 4 after implantation, due to increases in polar and neutral lipids. The lipid classes responding were phosphatidylcholine, phosphatidylinositol, phosphatidylethanolamine, sterols and sterol esters, in a proportion that approximately reflected the increase in plasma vitellogenin (VtG) levels as measured by a non-competitive enzyme-linked immunosorbent assay (ELISA). Plasma non-esterified fatty acids and triacylglycerol were not affected by E2 treatment. Plasma growth hormone GH levels were increased, and plasma somatostatin-14 (SRIF) levels decreased in E2-treated fish, responses which could be secondary to elevated plasma lipid (VtG) content, although a direct E2 action on somatotroph function is possible. Plasma T4 concentrations were not affected by E2 treatment, but plasma T3 concentrations were significantly lower than in controls 1 week after implantation when plasma E2 concentrations were the highest; this is in support of the hypothesis that E2 has a suppressive action on T3 production. |
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| Keywords: | neutral lipid oestrogen phospholipid polar lipid reproduction vitellogenin |
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