Ionoregulatory and endocrine responses to disturbed salt and water balance in Mozambique tilapia exposed to confinement and handling stress.
This study assessed the endocrine and ionoregulatory responses by tilapia (Oreochromis mossambicus) to disturbances of hydromineral balance during confinement and handling. In fresh water (FW), confinement and handling for 0.5, 1, 2 and 6h produced elevations in plasma cortisol and glucose; a reduction in plasma osmolality was observed at 6h. Elevations in plasma prolactins (PRL(177) and PRL(188)) accompanied this fall in osmolality while no effect upon growth hormone (GH) was evident; an increase in insulin-like growth-factor I (IGF-I) occurred at 0.5h. In seawater (SW), confinement and handling increased plasma osmolality and glucose between 0.5 and 6h; no effect on plasma cortisol was seen due to variable control levels. Concurrently, both PRLs were reduced in stressed fish with only transient changes in the GH/IGF-I axis. Next, the branchial expression of Na(+)/K(+)/2Cl(-) cotransporter (NKCC) and Na(+)/Cl(-) cotransporter (NCC) was characterized following confinement and handling for 6h. In SW, NKCC mRNA levels increased in stressed fish concurrently with elevated plasma osmolality and diminished gill Na(+), K(+)-ATPase activity; NCC was unchanged in stressed fish irrespective of salinity. Taken together, PRL and NKCC participate in restoring osmotic balance during acute stress while the GH/IGF-I axis displays only modest responses.
Breves
Jason P
JP
Hawaii Institute of Marine Biology, University of Hawaii, Kaneohe, HI 96744, USA.
Hirano
Tetsuya
T
Grau
E Gordon
EG
D000818:Animals; D001786:Blood Glucose / Q000378:metabolism; D004703:Endocrine System / Q000502:physiology*; D005618:Fresh Water; D005880:Gills / Q000201:enzymology; D013006:Growth Hormone / Q000097:blood; D006234:Handling, Psychological; D006854:Hydrocortisone / Q000097:blood; D007334:Insulin-Like Growth Factor I / Q000378:metabolism; D017136:Ion Transport; D009994:Osmolar Concentration; D011388:Prolactin / Q000097:blood; D012623:Seawater; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D017210:Tilapia / Q000097:blood / Q000502:physiology*; D013997:Time Factors; D014882:Water-Electrolyte Balance / Q000502:physiology*
D001786:Blood Glucose; D007334:Insulin-Like Growth Factor I; D011388:Prolactin; D013006:Growth Hormone; D000254:Sodium-Potassium-Exchanging ATPase; D006854:Hydrocortisone