PARENT SESSION
PT2 - Endocrine Disruption
Tuesday, 19 November 2002
8:00 AM to 6:30 PM
Exhibit Hall
(P551) o,p-DDT AND ITS METABOLITES ARE DECREASED BY TAMOXIFEN IN MATURE MALE TILAPIA.
Leaños-Castañeda, Olga*,1, Van der Kraak, Glen2, del Río-García, Marcela1, Ceja-Moreno, Victor1, Simá, Raul1, Gold, Gerardo1, 1 Departamento de Recursos del Mar, Cinvestav Unidad Mérida, Mérida, Yucatán, Mexico2 Zoology Department, Guelph University, Guelph, Ontario, Canada
ABSTRACT- DDT has been shown to be an endocrine disrupting chemical. Since tamoxifen is a useful drug to study the estrogenic endocrine disruptors, the interaction of o,p-DDT and tamoxifen on plasma levels of o,p-DDT, and its metabolites o,p-DDD and o,p.DDE in mature male tilapia was investigated. Tilapia was intraperitoneally treated with o,p-DDT 60 mg/kg (1 dose) and 40 mg/kg (6 doses) alone or with tamoxifen 5 mg/kg (7 doses) for 12 days. At the end of the exposure period, fish were anaesthetized and blood was taken to obtain plasma and Endosulfan II added as recovery standard. Samples were extracted and analyzed by GC/ECD. When tilapia was treated only with o,p-DDT 60 mg/kg and 240 mg/kg, the highest plasma concentration was for o,p-DDT at 1,926±343 ng/ml and 13,147±1547 ng/ml respectively and the less levels for its metabolites, o,p-DDD 150±23 ng/ml and 3,023±566 ng/ml, and o,p-DDE 18±3 ng/ml and 75±12 ng/ml being the lower levels for o,p-DDE. The combined treatment of o,p-DDT + tamoxifen significant decreased (about 50%) the concentrations of o,p-DDT (857±191 ng/ml, and 5,737±783 ng/ml), o,p-DDD (87±21 ng/ml, and 1,277±123ng/ml) and o,p-DDE (7±1ng/ml, and 26±5ng/ml, respectively) compared with o,p-DDT alone and the relative proportions remained the same. The decrease on o,p-DDT and its metabolites induced by tamoxifen suggests that tamoxifen might be increasing o,p-DDT and metabolites clearance, mainly mediated by changing the biotransformation. This o,p-DDT-tamoxifen interaction shows that the study of the effects induced by estrogenic endocrine disruptors is very complex, and even more so with tamoxifen, which presents estrogenic-antiestrogenic behavior.
Key words: DDT, endocrine disruption, tamoxifen, tilapia