Increased daylength stimulates plasma growth hormone and gill Na+, K+-ATPase in Atlantic salmon (Salmo salar) |
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Authors: | S D McCormick B Th Björnsson M Sheridan C Eilerlson J B Carey M O'Dea |
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Institution: | (1) Anadromous Fish Research Center, National Biological Service, P.O. Box 796, 04376 Turners Falls, MA, USA;(2) Department of Zoophysiology, Göteborg University, Sweden;(3) Department of Zoology, North Dakota State University, ND, USA;(4) Present address: Department of Anatomy and Cell Biology, Emory University, School of Medicine, Atlanta, GA, USA |
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Abstract: | Atlantic salmon juveniles reared at constant temperature (9–10°C) were exposed to four photoperiod treatment and sampled every 2 weeks from January through May. Fish reared under normal photoperiod exhibited eight-and three fold increases in plasma growth hormone and gill Na+, K+-ATPase activity, respectively, between January and April. Fish exposed to abrupt increases in daylength (LD 15:9) in February or March responded with earlier increases in plasma growth hormone and gill Na+, K+-ATPase activity, and earlier decreases in condition factor relative to fish in the normal photoperiod group. Fish maintained under short daylength (LD 9:15) from January to May exhibited delayed and muted increases in plasma growth hormone and gill Na+, K+-ATPase activity. Plasma thyroxine exhibited a 2.5-fold increase from February to late March in the normal photoperiod group, was generally lower in the LD 9:15 group, but exhibited no obvious response to abrupt increases in daylength. There was an increase in plasma 3,5,3 -triiodo-l-thyronine with time in all groups (43–80%) but no significant response to photoperiod. Plasma levels of somatostatin-25 were highest in the LD 9:15 group, but there was no detectable response to increased daylength in any of the photoperiod treatments. The results indicate that plasma growth hormone is responsive to increased daylength and may be causally related to subsequent increases in gill Na+, K+-ATPase.Abbreviations
ANOVA
two-way analysis of variance
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BCA
bicinchoninic acid
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BSA
Bovine serum albumin
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EDTA
ethylene diamine tetraacetic acid
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ELISA
enzyme-linked immunosorbent assay
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EST
eastern standard time
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GH
growth hormone
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GLU
Glucagen
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IgG
Immunoglobulin G
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INS
Insulin
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LDN
Simulated natural photoperiod
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RIA
radio immuno assay
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RIA
radio immuno assay
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SEI
Sucrose EDTA imidazole
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SS-25
somatostatin-25
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SW
sea water
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T
3
3,5,3 triiodo-l-thyronine
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T
4
thyroxine |
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Keywords: | Photoperiod Smolt Ion transport Thyroid hormones Somatolactin |
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