Opposite effects of 17 beta-estradiol and combined growth hormone-cortisol treatment on hypo-osmoregulatory performance in sea trout presmolts, Salmo trutta.
In March, sexually immature sea trout presmolts (Salmo trutta trutta) were injected every second day with saline, 2 micrograms 17 beta-estradiol (E2)/g, 2 micrograms ovine growth hormone (GH) + 6 micrograms cortisol (F)/g, or all three hormones (E2-GH-F) simultaneously. A SW-challenge test was performed after six injections. At the time of SW-transfer, high total plasma calcium levels in E2- and E2-GH-F-treated fish indicated activated vitellogenesis in these groups. All control, GH-F, and E2-GH-F-treated fish survived SW-transfer, whereas 43% of the E2-treated fish died after transfer. On Day 2 after transfer, there were marked differences among groups in their osmoregulatory response. Changes in ion-osmotic parameters (plasma Na+, Cl-, Mg2+, and total calcium and muscle water) indicated the following degree of osmotic stress: E2 greater than control greater than E2-GH-F greater than GH-F, which was inversely correlated with pretransfer gill Na+/K(+)-ATPase activity: GH-F greater than E2-GH-F greater than control greater than E2. On Day 7 after transfer there were no major differences among the groups with regard to plasma ions and muscle water content. The detrimental influence of elevated plasma E2 levels on hypo-osmo-regulatory physiology may indicate an important role of E2 during development.
Madsen
S S
SS
Institute of Biology, Odense University, Denmark.
Korsgaard
B
B
D000818:Animals; D002118:Calcium / Q000097:blood; D002712:Chlorides / Q000097:blood; D004347:Drug Interactions; D004573:Electrolytes / Q000097:blood*; D004958:Estradiol / Q000494:pharmacology*; D005260:Female; D005880:Gills / Q000201:enzymology; D013006:Growth Hormone / Q000494:pharmacology*; D006854:Hydrocortisone / Q000494:pharmacology*; D007700:Kinetics; D008274:Magnesium / Q000097:blood; D008297:Male; D009132:Muscles / Q000187:drug effects / Q000502:physiology*; D012964:Sodium / Q000097:blood; D000254:Sodium-Potassium-Exchanging ATPase / Q000378:metabolism; D013997:Time Factors; D014337:Trout / Q000502:physiology*; D014882:Water-Electrolyte Balance / Q000187:drug effects*
D002712:Chlorides; D004573:Electrolytes; D004958:Estradiol; D013006:Growth Hormone; D012964:Sodium; D000254:Sodium-Potassium-Exchanging ATPase; D008274:Magnesium; D002118:Calcium; D006854:Hydrocortisone