Osmoregulatory actions of insulin-like growth factor-I in rainbow trout (Oncorhynchus mykiss).
The ability of insulin-like growth factor-I (IGF-I), insulin and GH to promote hypoosmoregulatory ability was examined in juvenile rainbow trout (Oncorhynchus mykiss). Following adaptation to 12 parts per thousand (p.p.t.) seawater for 5 days, fish were given a single injection of hormone or vehicle, then exposed to 29 p.p.t. for 24 h and examined for changes in plasma osmolarity, ions and glucose. Ovine GH (oGH; 0.2 micrograms/g) significantly improved the ability of rainbow trout to maintain plasma osmolarity and sodium levels following transfer to 29 p.p.t. seawater. Recombinant bovine IGF-I (0.01, 0.05 and 0.02 micrograms/g) also improved the hypoosmoregulatory ability of trout; the effect being dose-dependent and greater than that of oGH. Bovine insulin (0.01, 0.05 and 0.2 micrograms/g) had no statistically significant effect on plasma ions. The results indicate that IGF-I is a potential mediator of the action of GH in seawater adaptation of salmonids.
McCormick
S D
SD
Department of Integrative Biology, California, Berkeley 94720.
Sakamoto
T
T
Hasegawa
S
S
Hirano
T
T
D000222:Adaptation, Physiological / Q000502:physiology; D000818:Animals; D013006:Growth Hormone / Q000502:physiology; D007328:Insulin / Q000502:physiology; D007334:Insulin-Like Growth Factor I / Q000502:physiology*; D009994:Osmolar Concentration; D011994:Recombinant Proteins / Q000502:physiology; D014337:Trout / Q000502:physiology*; D014882:Water-Electrolyte Balance / Q000502:physiology*
D007328:Insulin; D011994:Recombinant Proteins; D007334:Insulin-Like Growth Factor I; D013006:Growth Hormone