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Response of the salmon somatotropic axis to growth hormone administration under two different salinities

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Title: Response of the salmon somatotropic axis to growth hormone administration under two different salinities
Authors: Shimizu, Munetaka Browse this author →KAKEN DB
Fukada, Haruhisa Browse this author
Hara, Akihiko Browse this author →KAKEN DB
Dickhoff, Walton W. Browse this author
Keywords: insulin-like growth factor-I
growth hormone
Issue Date: 18-Dec-2007
Publisher: Elsevier
Journal Title: Aquaculture
Volume: 273
Issue: 2-3
Start Page: 320
End Page: 328
Publisher DOI: 10.1016/j.aquaculture.2007.10.013
Abstract: We compared the response of plasma insulin-like growth factor-I (IGF-I) to growth hormone (GH) administration under two different salinities to test the hypothesis that environmental salinity alters the "activity" of the GH-IGF-I axis. In July, postsmolt coho salmon reared in fresh water (FW) were transferred to either FW or half seawater (1/2 SW) (15 ppt) tank. During the experiment, water temperature was maintained at 10℃ for both salinities; photoperiod was adjusted to that of Seattle (48°N), and fish were not fed. Two days after transfer, fish were injected once with porcine GH (pGH) at a dose of 2 or 8 μg/g body weight. Liver and blood samples were collected 1, 2 and 3 days after injection. Liver GH receptor (GHR) mRNA expression was analyzed by quantitative real-time RT-PCR, and plasma IGF-I, 41-kDa IGF-binding protein (main carrier of IGF-I) and pGH were quantified by radioimmunoassays. Transfer to 1/2 SW resulted in transient increases in basal levels of liver GHR mRNA and 41 kDa IGF-binding protein (IGFBP) but not IGF-I. The GH-injection increased liver GHR mRNA, plasma IGF-I and 41-kDa IGFBP in fish in both FW and 1/2 SW. However, the time course and magnitude of the response differed between salinities. Fish in FW receiving 8 μg/g pGH had the highest IGF-I levels (63.7 ± 6.8 ng/ml) one day after injection, whereas fish in 1/2 SW showed a peak (88.8 ± 14.3 ng/ml) two days after injection of the same dose. It is speculated that the prolonged response to GH by fish in 1/2 SW may be due to slower disappearance of pGH from the circulation in fish in 1/2 SW. The transient increase in basal liver GHR mRNA may also contribute to a greater response for fish in 1/2 SW. These results suggest that salinity is capable of altering the "activity" of the GH-IGF-I axis in salmon.
Type: article (author version)
Appears in Collections:水産科学院・水産科学研究院 (Graduate School of Fisheries Sciences / Faculty of Fisheries Sciences) > 雑誌発表論文等 (Peer-reviewed Journal Articles, etc)

Submitter: 清水 宗敬

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