A pharmacokinetic study of p, p'-DDT and its metaolites during flight of the White-crowned sparrow, Zonotrichia leucophrys
Scollon, Edward J
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Historical use of DDT has led to the bioaccumulation of DDT and its metabolites in wildlife. Avian species have proven to be particularly susceptible. DDE-induced eggshell thinning has resulted in dramatic declines of many top-level predators such as the bald eagle, peregrine falcon, and brown pelican. Despite this drawback, DDT effectively controls vector-borne diseases carriers. Therefore, its use has continued in many tropical regions. Migratory birds can bioaccumulate DDT and other lipophilic compounds in their overwintering grounds in these tropical regions, especially 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, andp.p'-DDT loading on thyroid hormones, corticosterone, and residue metabolism and distribution in recently exposed white-crowned sparrows. Female sparrows were captured near Lubbock, Texas, and dosed with 5 mg p,p'- DDT per kg body weight over 3 d. Following 1 d of recovery, the sparrows were flown in a wind tunnel for up to 140 min in 15 min blocks. Food was withheld from the start of the flight period until the birds were euthanized. Consequently, birds which flew for 140 min fasted for up to 9 h. Control and fasting groups allowed measurement of hormone fluctuations and DDT metabolism not associated with DDT loading or flight. In the flown birds, corticosterone was elevated and T4 was depressed. Mean concentrations of T3 did not differ among any of the test groups. However, T3 and T4 plasma concentrations decreased over time in the flown and fasted groups. T4 decreased significantly in flown birds dosed with DDT, and T3 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 the rate of residue increase over time in any of tissues examined. When sparrows flew and fasted simultaneously, fasting still did not significantly contribute to an increase in 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, effectively demonstrating the potential for brief flights to enhance the mobilization of DDT and its metabolites.