Endocrine disruption mechanism of o,p'-DDT in mature male tilapia (Oreochromis niloticus).
The aim of the present study was to evaluate, in vivo, the potential of o,p'-DDT to disrupt the endocrine system of mature male tilapia. In particular, the possibility that o,p'-DDT effects were mediated directly via the estrogen receptor (ER). Compounds with known ability to bind to the ER were employed: estradiol to induce and tamoxifen to inhibit the estrogenic effects result of the activation of the ER. In addition, an aromatase inhibitor, 4-hydrxyandrostenedione (4-OHA), was used to assess the ability of o,p'-DDT to induce estrogenic effects in a surrounding of low estradiol concentration. The effects of estradiol and o,p'-DDT were studied alone or in the presence of tamoxifen or 4-OHA at the end of a 12-day period of exposure. The main endpoints measured were plasma alkaline-labile phosphorous (ALP; an indirect indicator of vitellogenin), estradiol, testosterone and o,p'-DDT. It was found that o,p'-DDT was able to induce the vitellogenesis (measured as plasma ALP increase) and decrease the circulating levels of estradiol and testosterone. Interestingly, o,p'-DDT kept this ability in whole fish with low concentrations of estradiol which would exclude endogenous estradiol as indirect mediator of the estrogenic effects induced by o,p'-DDT. In addition, the plasma concentration of o,p'-DDT, instead of that of estradiol, was closely related to the plasma ALP increase induced by o,p'-DDT. This indicates that o,p'-DDT could have directly activated the vitellogenesis. The antiestrogenic action of tamoxifen to inhibit the vitellogenesis and the decrease on plasma estradiol induced by o,p'-DDT indicates that o,p'-DDT can bind directly to the ER. In conclusion, this in vivo study shows that o,p'-DDT has the potential to disrupt the endocrine system and strongly supports that the estrogenic actions of o,p'-DDT involve binding to the ER.
Leaños-Castañeda
Olga
O
Department of Integrative Biology, University of Guelph, Ontario, Canada. olgalidia09@yahoo.com
van der Kraak
Glen
G
Rodríguez-Canul
Rossanna
R
Gold
G
G
D000818:Animals; D003634:DDT / Q000633:toxicity*; D052244:Endocrine Disruptors / Q000633:toxicity*; D004958:Estradiol / Q000097:blood; D008297:Male; D011960:Receptors, Estrogen / Q000187:drug effects; D013739:Testosterone / Q000097:blood; D017210:Tilapia
D052244:Endocrine Disruptors; D011960:Receptors, Estrogen; D013739:Testosterone; D004958:Estradiol; D003634:DDT