Evidence for growth hormone/insulin-like growth factor I axis regulation of seawater acclimation in the euryhaline teleost Fundulus heteroclitus.
The ability of ovine growth hormone (oGH), recombinant bovine insulin-like growth factor I (rbIGF-I), recombinant human insulin-like growth factor II (rhIGF-II), and bovine insulin to increase hypoosmoregulatory capacity in the euryhaline teleost Fundulus heteroclitus was examined. Fish acclimated to brackish water (BW, 10 ppt salinity, 320 mOsm/kg H2O) were injected with a single dose of hormone and transferred to seawater (SW, 35 ppt salinity, 1120 mOsm/kg H2O) 2 days later. Fish were sampled 24 h after transfer and plasma osmolality, plasma glucose, and gill Na+, K+-ATPase activity were examined. Transfer from BW to SW increased plasma osmolality and gill Na+,K+-ATPase activity. Transfer from BW to BW had no effect on these parameters. rbIGF-I (0.05, 0.1, and 0.2 microg/g) improved the ability to maintain plasma osmolality and to increase gill Na+, K+-ATPase activity in a dose-dependent manner. oGH (0.5, 1, and 2 microg/g) also increased hypoosmoregulatory ability but only the higher doses (2 microg/g) significantly increased gill Na+,K+-ATPase activity. oGH (1 microg/g) and rbIGF-I (0.1 microg/g) had a significantly greater effect on plasma osmolality and gill Na+,K+-ATPase activity than either hormone alone. rhIGF-II (0.05, 0.1, and 0.2 microg/g) and bovine insulin (0.01 and 0.05 microg/g) were without effect. The results suggest a role of GH and insulin-like growth factor I (IGF-I) in seawater acclimation of F. heteroclitus. Based on these findings and previous studies, it is concluded that the capacity of the GH/IGF-I axis to increase hypoosmoregulatory ability may be a common feature of euryhalinity in teleosts.
Departamento de Biología Animal, Facultad de Ciencias del Mar, Universidad de Cádiz, Puerto Real, Cádiz, 11510, Spain.
J M
JM
Mancera
S D
SD
McCormick
D000222:Adaptation, Physiological / Q000187:drug effects*; D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D004305:Dose-Response Relationship, Drug; D005500:Follow-Up Studies; D005880:Gills / Q000187:drug effects / Q000201:enzymology; D013006:Growth Hormone / Q000494:pharmacology*; D007328:Insulin / Q000494:pharmacology; D007334:Insulin-Like Growth Factor I / Q000494:pharmacology*; D007335:Insulin-Like Growth Factor II / Q000494:pharmacology; D007695:Killifishes / Q000502:physiology*; D009994:Osmolar Concentration; D011994:Recombinant Proteins; D012623:Seawater; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism
D001786:Blood Glucose; D007328:Insulin; D011994:Recombinant Proteins; D007334:Insulin-Like Growth Factor I; D007335:Insulin-Like Growth Factor II; D013006:Growth Hormone; D000254:Sodium-Potassium-Exchanging ATPase