17beta-Estradiol affects osmoregulation in Fundulus heteroclitus.
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.
Departamento de Biología, Facultad de Ciencias del Mar y Ambientales, Universidad de Cádiz, Puerto Real, Cádiz 11510, Spain. juanmiguel.mancera@uca.es
Juan Miguel
JM
Mancera
Marcel
M
Smolenaars
Raúl
R
Laiz-Carrión
María del Pilar
Mdel P
Martín del Río
S E Wendelaar
SE
Bonga
Gert
G
Flik
D009597:4-Nitrophenylphosphatase / Q000378:metabolism; D000818:Animals; D002712:Chlorides / Q000097:blood; D004305:Dose-Response Relationship, Drug; D004958:Estradiol / Q000008:administration & dosage / Q000494:pharmacology*; D023781:Fundulidae / Q000502:physiology*; D005880:Gills / Q000201:enzymology; D012964:Sodium / Q000097:blood; D014882:Water-Electrolyte Balance / Q000187:drug effects*
D002712:Chlorides; D004958:Estradiol; D012964:Sodium; D009597:4-Nitrophenylphosphatase