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Response of the salmon somatotropic axis to growth hormone administration under two different salinities
- Source :
-
Aquaculture . Dec2007, Vol. 273 Issue 2/3, p320-328. 9p. - Publication Year :
- 2007
-
Abstract
- 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 °C 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. [Copyright &y& Elsevier]
- Subjects :
- *SOMATOTROPIN
*SOMATOMEDIN
*WATER temperature
*SALMON
Subjects
Details
- Language :
- English
- ISSN :
- 00448486
- Volume :
- 273
- Issue :
- 2/3
- Database :
- Academic Search Index
- Journal :
- Aquaculture
- Publication Type :
- Academic Journal
- Accession number :
- 27783790
- Full Text :
- https://doi.org/10.1016/j.aquaculture.2007.10.013