Keywords :
Adaptation, Physiological; Animals; Binding, Competitive; Carrier Proteins/metabolism; Chromatography, High Pressure Liquid; Fish Proteins; Glycoproteins/metabolism; Growth Hormone/metabolism; Iodine Radioisotopes; Oncorhynchus mykiss/blood; Pituitary Hormones/metabolism; Precipitin Tests; Receptors, Somatotropin/metabolism; Recombinant Proteins; Seawater
Abstract :
[en] A soluble protein that specifically bound 125I-human growth hormone (hGH) was identified in rainbow trout plasma, using HPLC-gel filtration. The binding affinity of the protein for hGH was 1.2 x 10(9)M-1. 125I-rainbow trout GH (tGH) was also able to bind to the protein albeit with a lower affinity (6.6 x 10(7)M-1) than hGH. Crosslinking experiments using 125I-hGH revealed two specific bands of 150 and 130 kDa. The complex 125I-hGH-BP could be precipitated by a monoclonal anti-GH receptor antibody, suggesting a close relationship between the plasma GH-BP and the GH receptor. A fourfold increase in the hGH binding to the GH-BP was shown 48 h after transfer of the fishes from freshwater to seawater. The increase in binding was related to a high binding capacity without significant changes in binding affinity. These results suggest a potential role of this related GH-BP as an index of GH effects during seawater adaptation in salmonids.
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