| DDT is used in many tropical regions of the world for vector control. Migratory birds overwintering in these tropical regions can bioaccumulate DDT, especially just prior to migration when their lipid reserves are greatest. Therefore, there is a need to understand the metabolism and disposition of DDT during a migratory flight. This study was conducted to evaluate the interactions of flight, fasting, and p,p-DDT loading on thyroid hormones, corticosterone, and residue metabolism and distribution in recently exposed white crowned sparrows.; Female sparrows were dosed with 5 mg/kg p,p-DDT every day for 3 d. On day 5, the sparrows were flown in a wind tunnel for up to 140 min in 15 min blocks. Food was withheld at the initiation of the flights until the birds were euthanized. Consequently, birds which flew for 140 min, may have fasted for up to 9 h.; In the flown birds, corticosterone was elevated and thyroxine was depressed. Elevated corticosterone resulted from inadequate flight training, likely decreasing thyroid hormone production through negative feedback. Mean concentrations of triiodothyronine did not differ among any of the test groups. However, triiodothyronine and thyroxine plasma concentrations decreased over time in the flown and fasted groups. Thyroxine decreased significantly in flown birds dosed with DDT, and triiodothyronine decreased significantly in the fasted birds dosed with DDT.; DDT, DDD, and DDE were present in all of the tissues examined. DDMU, DDNU, and DDOH were not found. Fasting for up to 10 h did not significantly affect metabolite concentration in any of tissues examined. When sparrows were subjected to flight and fasting simultaneously, fasting still did not significantly contribute to tissue residues. However, the length of time flown was significantly correlated with increasing concentrations of DDT and DDD in the brain, and DDT, DDD, and DDE in the kidney.; This study demonstrates (1) the potential for DDT to disrupt thyroid hormones in stressed birds; (2) that brief flights enhance the mobilization of DDT and its metabolites; and (3) the first clear example that brief flights enhance the accumulation of DDT and its metabolites in brain. |
