Influence of persistent organic pollutants on the endocrine stress response in free-living and captive red kites (<i>Milvus milvus</i>)

Persistent organic pollutants (POPs) have the potential to impair the endocrine regulation of organisms and alter their ability to respond to environmental changes. We studied whether polychlorinated bi-phenyls (PCBs) and organochlorine pesticides (OCPs) affected the endocrine regulation of free-living and captive red kites (Milvus milvus) through studying the dynamics of corticosterone (CORT) and dehydroepiandrosterone (DHEA). We sampled migratory free-living kites coming from northern Europe and captive kites born in a rehabilitation center in Spain. We used body feathers from the interscapular region as a minimally-invasive and integrative matrix. The most abundant compound detected in freel-iving kites was 4,4'-dichlorodiphenyldichloroethylene (4,4'-DDE; 6.10 +/- 1.56 ng g(-1) dw feather) followed by CB-153 (3.10 +/- 0.63 ng g(-1) dw feather) and CB-180 (2.43 +/- 1.08 ng g(-1) dw feather). In captive kites, the most abundant compounds were 4,4'-dichlorodyphenyltrichloroethane (4,4'-DDT; 2.38 +/- 1.30 ng g(-1) dw feather), CB-153 (2.15 +/- 0.47 ng g(-1) dw feather) and hexachlorobenzene (HCB; 2.03 +/- 0.45 ng g(-1) dw feather) at similar concentrations. Free-living kites showed higher levels of 4,4'-DDE and CB-180 in comparison to captive kites. Age influenced HCB and CB-101 levels, whereas body mass was inversely related to CB-180 and 4,4'-DDT. Interestingly, captive kites showed a ratio DDT/DDE higher than 1 suggesting a relatively recent exposure of DDT, in contrast to free-living kites. Regarding hormonal levels, free-living kites showed higher levels of CORT (3.30 +/- 0.22 pg mm(-1) feather) than captive (2.40 +/- 0.16 pg mm(-1) feather), reflecting higher allostatic load. In addition, a positive association between PCBs and DDTs and adrenal hormones was found in free-living kites, suggesting an increase of CORT as a response of the endocrine system to cope with stressors and a subsequent elevation of DHEA to ameliorate the potential negative effects that high CORT levels could cause to the organism. (C) 2018 Elsevier Ltd. All rights reserved.