PARENT SESSION
PT2 - Endocrine Disruption
Tuesday, 19 November 2002
8:00 AM to 6:30 PM
Exhibit Hall

(P550) EFFECTS OF DDT ISOMERS ON TESTOSTERONE AND ESTRADIOL PLASMA CONCENTRATIONS IN FEMALE TILAPIA.

Leaños-Castañeda, Olga^*,1, Van der Kraak, Glen², Lister, Andrea², 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 isomers can induce endocrine disruption by two different mechanism of action: o,p-DDT acts as estrogenic compound while p,p-DDT acts as antiandrogenic. In order to investigate if the two DDT isomers induce different effects during an ovarian cycle in female tilapia, the temporal course of gonadosomatic index (GSI), plasma testosterone and estradiol were measured at 0, 4, 8, 12, and 16 days after the females spawned. Females were divided into three experimental groups: vehicle control (corn oil), o,p-DDT (60 mg/kg), and p,p-DDT (60 mg/kg). All the treatments were given intraperitoneally at 0 day (except females sacrificed at 0 day). After spawning at 0, 4, 8, 12, and 16 days, samples of plasma and gonads were obtained, in order to determine estradiol, testosterone and GSI. GSI in the control group increased with time 1.53±0.09, 1.87±0.37, 3.68±0.45, 4.64±0.8 and 5.88±0.58. When o,p-DDT treatment was given the highest GSI (6.24±0.34) was reached at 12 days while p,p-DDT did not change GSI compared with control group. Temporal course of plasma estradiol and testosterone showed the same pattern characterized by low levels (1.8±0.7g/ml and 2.8±0.6g/ml) at day 0, increased (4.8±1.1g/ml and 4.2±0.7g/ml) at day 4, the highest levels (8.5±2g/ml and 10.3±3g/ml) were observed at day 8, and then decreased at days 12 (2.8±1.4g/ml and 4.2±1.2g/ml) and 16 (2.1±0.8g/ml and 4.5±2.2g/ml, respectively). o,p-DDT and p,p-DDT produced a significant decreased of the estradiol peak (2.5±0.6g/ml and 3.4±1.7g/ml, respectively) at day 8 and then decreased with o,p-DDT treatment (0.49±0.15g/ml) while increased with p,p-DDT (4.5±1.1g/ml) at day 16. The pattern of temporal course of testosterone was different in p,p-DDT group as compared with the control group, with the highest levels at day 16 (16.2±5.4g/ml). In conclusion, DDT isomers induced different changes on estradiol and testosterone without evident effects on gonadal development (measured only by GSI) during an ovarian cycle in tilapia.

Key words: DDT, endocrine disruption, estradiol, testosterone