open access

https://hdl.handle.net/2115/38998

Measurement of circulating salmon IGF binding protein-1 : assay development, response to feeding ration and temperature, and relation to growth parameters

Salmon IGFBP-1 RIA

英語

condition factor

2006-01

Society for Endocrinology

Journal of Endocrinology

188(1)

101-110

Fish plasma/serum contains multiple insulin-like growth factor binding proteins (IGFBPs), although their identity and physiological regulation are poorly understood. In salmon plasma, at least three IGFBPs with molecular masses of 22, 28 and 41 kDa are detected by Western ligand blotting. The 22-kDa IGFBP has recently been identified as a homolog of mammalian IGFBP-1. In the present study, a radioimmunoassay (RIA) for salmon IGFBP-1 was established and regulation of IGFBP-1 by food intake and temperature, and changes in IGFBP-1 during smoltification were examined. Purified IGFBP-1 from serum was used for standard, tracer preparation and antiserum production. Crosslinking 125I-IGFBP-1 with salmon IGF-I eliminated interference by IGFs. The RIA had little cross-reactivity with salmon 28- and 41-kDa IGFBPs (< 0.5%) and measured IGFBP-1 as low as 0.1 ng/ml. Fasted fish had significantly higher IGFBP-1 levels than fed fish (21.6 ± 4.6 ng/ml vs 3.0 ± 2.2 ng/ml). Plasma IGFBP-1 was measured in individually tagged one-year old coho salmon reared for 10 weeks under four different feeding regimes as follows: high constant (2% body weight/day), medium constant (1% body weight/day), high variable (2% body weight/day - 0.5% body weight/day) and medium variable (1% body weight/day - 0.5% body weight/day). Fish fed with high ration had lower IGFBP-1 than those with medium ration. Circulating IGFBP-1 increased following a drop in feeding ration to 0.5% and returned to the basal levels when feeding ration was increased. Another group of coho salmon were reared for nine weeks under different water temperatures (11℃ or 7℃) and feeding rations (1.75, 1 or 0.5% body weight/day). Circulating IGFBP-1 levels were separated by temperature during the first four weeks; a combined effect of temperature and feeding ration was seen in week seven; only feeding ration influenced IGFBP-1 level thereafter. These results indicate that IGFBP-1 is responsive to moderate nutritional and temperature changes. There was a clear trend that circulating IGFBP-1 levels were negatively correlated with body weight, condition factor (body weight/body length3 x 100), growth rates and circulating 41-kDa IGFBP levels but not IGF-I levels. During parr-smolt transformation of coho salmon, IGFBP-1 levels showed a transient peak in late April, which was opposite to changes in condition factor. Together, these findings suggest that salmon IGFBP-1 is inhibitory to IGF-action. In addition, IGFBP-1 responds to moderate changes in dietary ration and temperature, and shows a significant negative relationship to condition factor.

学術雑誌論文

Accepted Manuscript

Disclaimer. This is not the definitive version of record of this article. This manuscript has been accepted for publication in Journal of Endocrinology, but the version presented here has not yet been copy edited, formatted or proofed. Consequently, the Society for Endocrinology accepts no responsibility for any errors or omissions it may contain. The definitive version is now freely available at http://dx.doi.org/10.1677/joe.1.06475 © 2006 Society for Endocrinology.

0022-0795

1479-6805

AA00697140