title: Development of a time-resolved fluoroimmunoassay for salmon insulin-like growth factor binding protein-1b.
abstract: In salmon plasma/serum, three major insulin-like growth factor binding proteins (IGFBPs) are consistently detected at 22-, 28- and 41-kDa. The 22-kDa form has been identified as IGFBP-1b and shown to increase under catabolic conditions. We developed a competitive time-resolved fluoroimmunoassay (TR-FIA) for salmon IGFBP-1b. Purified salmon IGFBP-1b was used for biotin-labeling, assay standard and antiserum production. The TR-FIA did not cross-react with the 41-kDa form (IGFBP-2b) but showed 3% cross-reactivity with the 28-kDa form (IGFBP-1a). It measured IGFBP-1b levels as low as 0.4 ng/ml, and ED80 and ED20 were 0.9 and 24.6 ng/ml, respectively. There appears to be little interference by IGF-I. Using the TR-FIA, serum IGFBP-1b levels were measured in individually-tagged underyearling masu salmon fed or fasted for 5 weeks, or fasted for 3 weeks followed by refeeding for 2 weeks. Fasting for 3 weeks significantly increased circulating IGFBP-1b levels, while it returned to the basal levels after prolonged fasting for additional 2 weeks. Serum IGFBP-1b level negatively correlated with body weight, condition factor, specific growth rate and serum IGF-I level. During parr-smolt transformation of masu salmon, average circulating IGFBP-1b levels were the highest in May. There was a positive correlation between serum IGFBP-1b and IGF-I, which is in contrast to that in the fasting/feeding experiment. IGFBP-1b also showed a positive relationship with gill Na(+), K(+)-ATPase activity. These results suggest that the relationship between circulating IGFBP-1b and IGF-I during smoltification differs from that during fasting and IGFBP-1b may play a role in the development of hypoosmoregulatory ability.
authors.affiliation: Faculty of Fisheries Sciences, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido 041-8611, Japan.
authors.forename: Miki
authors.initials: M
authors.lastname: Fukuda
authors.affiliation: Faculty of Fisheries Sciences, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido 041-8611, Japan.
authors.forename: Nobuto
authors.initials: N
authors.lastname: Kaneko
authors.affiliation: Faculty of Fisheries Sciences, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido 041-8611, Japan.
authors.forename: Kohei
authors.initials: K
authors.lastname: Kawaguchi
authors.affiliation: National Institute of Nutrition and Seafood Research, PO Box 2029, Nordnes, N-5817 Bergen, Norway.
authors.forename: Ernst M
authors.initials: EM
authors.lastname: Hevrøy
authors.affiliation: Faculty of Fisheries Sciences, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido 041-8611, Japan.
authors.forename: Akihiko
authors.initials: A
authors.lastname: Hara
authors.affiliation: Faculty of Fisheries Sciences, Hokkaido University, 3-1-1 Minato, Hakodate, Hokkaido 041-8611, Japan. Electronic address: mune@fish.hokudai.ac.jp.
authors.forename: Munetaka
authors.initials: M
authors.lastname: Shimizu
mesh_terms: D000818:Animals; D015153:Blotting, Western; D005455:Fluorescent Antibody Technique / Q000379:methods*; D018970:Insulin-Like Growth Factor Binding Protein 1 / Q000097:blood*; D012474:Salmon; D013997:Time Factors
chemical_list: D018970:Insulin-Like Growth Factor Binding Protein 1
keywords: Fasting; Growth; Immunoassay; Insulin-like growth factor binding protein; Salmon; Smoltification