Androgen effects on plasma GH, IGF-I, and 41-kDa IGFBP in coho salmon (Oncorhynchus kisutch).
Among many species of salmonids, fast growing fish mature earlier than slow growing fish, and maturing males grow faster than non-maturing ones. To study the potential endocrine basis for this reciprocal relationship we examined the in vivo effects of the androgens, testosterone (T) and 11-ketotestosterone (11-KT), on plasma growth hormone (GH), insulin-like growth factor-I (IGF-I) and 41-kDa IGF binding protein (41-kDa IGFBP) (putative IGFBP-3) in coho salmon, Oncorhynchus kisutch. Immature male and female, two-year old fish (avg. wt. 31.7 +/- 0.63 g) were injected with coconut oil containing T or 11-KT at a dose of 0.1, 0.25, or 1 microg/g body weight. Blood samples were taken 1 and 2 weeks postinjection, and analyzed by immunoassay for T, 11-KT, GH, IGF-I, and 41-kDa IGFBP. Steroid treatments elevated the plasma T and 11-KT levels to physiological ranges typical of maturing fish. Plasma IGF-I and 41-kDa IGFBP levels increased in response to both T and 11-KT in a significant and dose-dependent manner after 1 and 2 weeks, but GH levels were not altered. These data suggest that during reproductive maturation, in addition to the previously demonstrated effects of the IGFs on steroidogenesis, the gonadal steroids may in turn play a significant role in regulating IGF-I and its binding proteins in fish. The interaction between the reproductive and growth axes may provide a regulatory mechanism for bringing about the dimorphic growth patterns observed between maturing and non-maturing salmonids and other species of fish.
Larsen
Donald A
DA
Integrative Fish Biology Program, Northwest Fisheries Science Center, NOAA Fisheries, 2725 Montlake Blvd E, Seattle, Washington 98112, USA. don.larsen@noaa.gov
Shimizu
Munetaka
M
Cooper
Kathleen A
KA
Swanson
Penny
P
Dickhoff
Walton W
WW
D000728:Androgens / Q000008:administration & dosage / Q000097:blood / Q000494:pharmacology*; D000818:Animals; D004305:Dose-Response Relationship, Drug; D005260:Female; D013006:Growth Hormone / Q000097:blood*; D007267:Injections; D018972:Insulin-Like Growth Factor Binding Protein 3 / Q000378:metabolism*; D007334:Insulin-Like Growth Factor I / Q000378:metabolism*; D008297:Male; D017684:Oncorhynchus kisutch / Q000502:physiology*; D013739:Testosterone / Q000008:administration & dosage / Q000031:analogs & derivatives* / Q000097:blood / Q000494:pharmacology*; D013997:Time Factors
D000728:Androgens; D018972:Insulin-Like Growth Factor Binding Protein 3; D013739:Testosterone; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone; C003600:11-ketotestosterone