Meeting Abstract

44.3  Jan. 6  Effects of environmental estrogens on osmoregulatory homeostasis and endocrine responses of euryhaline teleosts LERNER, D.T.*; DAVIS, L.K.; MCCORMICK, S.D.; HIRANO, T.; GRAU, E.G.; Hawaii Inst. of Marine Biol., Univ. of Hawaii, Kaneohe; Hawaii Inst. of Marine Biol., Univ. of Hawaii, Kaneohe; USGS, Conte Anadromous Fish Res. Cntr, Turners Falls, MA; Hawaii Inst. of Marine Biol., Univ. of Hawaii, Kaneohe; Hawaii Inst. of Marine Biol., Univ. of Hawaii Kaneohe dlerner@forwild.umass.edu

Mozambique tilapia and Atlantic salmon are euryhaline fishes widely used as models for examining hormonal control of ion regulation in fish. We examined the effects of nonylphenol (NP), a xenoestrogen, and estradiol (E2) on the maintenance of osmoregulatory homeostasis and endocrine responses in FW- and SW-adapted fishes. Tilapia received two intraperitoneal (ip) injections with either E2 (5 mg/kg), NP (150 mg/kg), or vehicle (vegetable oil). Atlantic salmon in FW received three ip injections with either E2 (2 mg/kg), NP (150 mg/kg), or vehicle. SW-acclimated salmon received a slow release implant of E2 (30 mg/kg in 1:1 solution of Crisco and vegetable oil). In tilapia, plasma GH, IGF-I and chloride, and gill Na⁺,K⁺-ATPase (NKA) were not affected at either salinity. E2 and NP reduced liver GH receptor (GHR) mRNA 50% in FW; only E2 had this effect in SW. In gill tissue, NP and E2 increased GHR mRNA in FW and SW, respectively. E2 and NP reduced liver IGF-I mRNA 25-50% in FW; only E2 had this effect in SW. In gill tissue, NP and E2 increased IGF-I mRNA 50-100% in FW and had no effect in SW. In Atlantic salmon, E2 and NP decreased plasma GH 3-6 fold in FW and E2 increased GH 4-fold in SW. Plasma IGF-I was decreased more than 50% in FW and SW. E2 reduced NKA in SW and ion regulatory ability in FW and SW; there was no affect of NP. E2 and NP decreased liver and gill GHR binding activity 2-3 fold in FW and SW. These data suggest that estrogenic compounds alter the GH/IGF-I axis and in some teleosts, this may compromise ion regulatory capacity.