title: Effects of o,p'-DDE, heptachlor, and 17beta-estradiol on vitellogenin gene expression and the growth hormone/insulin-like growth factor-I axis in the tilapia, Oreochromis mossambicus.
abstract: Effects of two endocrine disruptors, o,p'-DDE and heptachlor, and 17beta-estradiol (E(2)) on vitellogenin (Vg) and the growth hormone (GH)/insulin-like growth factor-I (IGF-I) axis were examined in male tilapia. In the first experiment, fish were given 5 weekly injections of either E(2), o,p'-DDE or heptachlor (5 microg/g). E(2) treatment increased plasma Vg and hepatic expression of three Vg genes (Vgs A, B, and C) and estrogen receptor alpha (ERalpha), while reducing plasma levels of IGF-I and suppressing the expression of IGF-I, the GH receptor (GHR2) and the putative somatolactin receptor (GHR1). Neither pesticide greatly affected the other parameters examined, except for a significant reduction in expression of GHR2 and increased plasma IGF-I. In the second experiment, fish were given a single injection of o,p'-DDE or heptachlor (100 microg/g), or E(2) (5 microg/g) and sacrificed 5 days post-injection. Treatment with E(2) stimulated expression of all three Vg genes. Both o,p'-DDE and heptachlor increased expression of VgB, whereas only o,p'-DDE increased VgA expression. There was no effect of o,p'-DDE or heptachlor on VgC expression or plasma Vg levels. Treatment with o,p'-DDE and heptachlor as well as E(2) increased ERalpha and ERbeta transcript levels. Similarly, both pesticides increased GHR1 and IGF-I expression, whereas no significant effect of E(2) was observed on GHR1, GHR2 or IGF-I expression. These results indicate that o,p'-DDE and heptachlor have varying temporal and dose effects on modulation of Vg and the GH/IGF-I axis that are distinct from E(2).
authors.affiliation: Hawaii Institute of Marine Biology, Department of Zoology, University of Hawaii, Kaneohe, HI 96744, USA.
authors.forename: Lori K
authors.initials: LK
authors.lastname: Davis
authors.forename: Nancy
authors.initials: N
authors.lastname: Visitacion
authors.forename: Larry G
authors.initials: LG
authors.lastname: Riley
authors.forename: Naoshi
authors.initials: N
authors.lastname: Hiramatsu
authors.forename: Craig V
authors.initials: CV
authors.lastname: Sullivan
authors.forename: Tetsuya
authors.initials: T
authors.lastname: Hirano
authors.forename: E Gordon
authors.initials: EG
authors.lastname: Grau
mesh_terms: D000818:Animals; D004958:Estradiol / Q000494:pharmacology*; D013006:Growth Hormone / Q000097:blood*; D006533:Heptachlor / Q000494:pharmacology*; D007334:Insulin-Like Growth Factor I / Q000096:biosynthesis*; D008297:Male; D008939:Mitotane / Q000031:analogs & derivatives* / Q000494:pharmacology; D017210:Tilapia / Q000378:metabolism*; D014819:Vitellogenins / Q000235:genetics*
chemical_list: D014819:Vitellogenins; D004958:Estradiol; D007334:Insulin-Like Growth Factor I; D008939:Mitotane; D006533:Heptachlor; D013006:Growth Hormone; C054919:2,2-(2-chlorophenyl-4'-chlorophenyl)-1,1-dichloroethene