title: Differential sensitivity of zonagenesis and vitellogenesis in Atlantic salmon (Salmo salar L) to DDT pesticides.
abstract: In Atlantic salmon (Salmo salar L) female sexual maturation entails both zonagenesis and vitellogenesis, both of which are controlled by increasing levels of estradiol-17 beta (E2). Antibodies against salmon zona radiata proteins (eggshell zr-proteins) and vitellogenin were used to monitor induction of oogenesis in juvenile salmon. Molecular weights of zr-monomers were estimated to about 66, 61, and 55 kDa, and to about 180 kDa for vitellogenin. Xenobiotics such as the pesticide DDT impair biological reproduction. The o,p'-DDT (1,1,1-trichloro-2[2-chlorophenyl]-2-[4-chlorophenyl]ethane) isomer seems to be a xenoestrogen. Serum levels of zr-proteins and vitellogenin, and hepatocytic biosynthesis of these components, were determined after in vivo treatment of salmon with DDT (technical, p,p'-(1,1,1-trichloro-2,2-bis[4-chlorophenyl]ethane) or o,p'-DDT) or E2. Exposing fish to frequent doses of o,p'-DDT (25 mg/kg b.w. (body weight) twice a week, six times totally) resulted in induction of all three zr-protein monomers, but not of vitellogenin. In contrast, three weekly injection of 10 mg/kg b.w. of either of the three DDT preparations did not induce typical zr-proteins or vitellogenin in serum. In vivo studies with combined DDT + E2 injections showed that none of the DDT preparations influenced E2-induced biosynthesis of zr-proteins or vitellogenin. E2 induction of these oogenetic processes was not blocked even by a high concentration (125 mg/kg b.w.) of o,p'-DDT. Furthermore, pretreatment of salmon with o,p'-DDT for 2 weeks, followed by one injection of E2, did not antagonize biosynthesis of zr-proteins, but serum concentration of vitellogenin was decreased. The data indicate that in juvenile salmon o,p'-DDT may be xenoestrogenic with regard to zonagenesis, but weakly anti-(xeno)estrogenic with regard to vitellogenesis. These findings suggest new complexities in fish reproductive toxicology of xenoestrogens. Compared to vitellogenesis, zonagenesis is a more sensitive parameter for monitoring reproductive effects of xenoestrogens.
authors.affiliation: Department of Molecular Biology, University of Bergen, HIB, Norway. trine.celius@mbi.uib.no
authors.forename: T
authors.initials: T
authors.lastname: Celius
authors.forename: B T
authors.initials: BT
authors.lastname: Walther
mesh_terms: D000818:Animals; D003634:DDT / Q000633:toxicity*; D004527:Egg Proteins / Q000096:biosynthesis*; D004958:Estradiol / Q000494:pharmacology; D005260:Female; D007306:Insecticides / Q000633:toxicity; D008099:Liver / Q000187:drug effects / Q000378:metabolism*; D012474:Salmon / Q000502:physiology*; D014819:Vitellogenins / Q000096:biosynthesis*; D015044:Zona Pellucida / Q000187:drug effects / Q000378:metabolism*
chemical_list: D004527:Egg Proteins; D007306:Insecticides; D014819:Vitellogenins; D004958:Estradiol; D003634:DDT