Fatty acid and lipid class composition in eyes and brain from teleosts and elasmobranchs |
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Authors: | Stoknes Iren S Økland Hege M W Falch Eva Synnes Marianne |
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Institution: | Departamento de Biología, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, Puerto Real, Cádiz 11510, Spain. juanmiguel.mancera@uca.es |
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Abstract: | The effect of 17beta-estradiol (E(2)) on osmoregulatory performance was examined in the euryhaline killifish, Fundulus heteroclitus. Fish were injected once with 1, 2 and 5 microg g(-1) E(2) and, 6 h after injection, transferred from 1 ppt seawater (SW) to full strength SW (40 ppt) or from SW to 1 ppt SW. In another set of experiments, fish were injected four times on alternate days with 2 microg g(-1) E(2) and then, 6 h after the last injection, transferred from 1 ppt SW to SW or from SW to 1 ppt SW. Fish were sampled 18 h after transfer (i.e., 24 h post-injection), and plasma osmolality, Na(+) and Cl(-) concentration and gill K(+)-pNPPase activity (a reflection of the sodium pump) were examined. Transfer from 1 ppt SW to SW resulted in significantly increased plasma osmolality, but did not affect gill K(+)-pNPPase activity. A single dose of E(2) (1, 2 and 5 microg g(-1)) prior to transfer from 1 ppt SW to SW increased plasma osmolality and decreased gill K(+)-pNPPase activity in a dose-dependent manner. Prolonged treatment with E(2) increased plasma osmolality and decreased gill K(+)-pNPPase activity in 1 ppt SW-adapted fish. Transfer of fish thus treated from 1 ppt SW to SW increased plasma osmolality and did not alter gill K(+)-pNPPase activity. Transfer from SW to 1 ppt SW had no significant effect on plasma osmolality or gill K(+)-pNPPase activity. Only the highest single dose of E(2) (5 microg g(-1)) prior to transfer from SW to 1 ppt SW decreased gill K(+)-pNPPase activity. Prolonged treatment with 2 microg g(-1) E(2) decreased gill K(+)-pNPPase activity only following transfer from SW to 1 ppt SW. The results substantiate an inhibitory action of E(2) on hypoosmoregulatory capacity in this euryhaline teleost. |
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