Changes in cytochrome P4501A activity during development in common tern chicks fed polychlorinated biphenyls, as measured by the caffeine breath test

Abstract

AbstractCytochrome P4501A (CYP1A) activity is often used as a biomarker of exposure of wildlife to polyhalogenated diaromatic hydrocarbons and is usually measured ex vivo in liver tissue. A caffeine breath test (CBT) with radiolabeled substrate (14C‐caffeine) was used to measure in vivo CYP1A activity twice during development in 14 common tern (Sterna hirundo) chicks treated with polyhalogenated diaromatic hydrocarbons. Tern hatchlings were fed fish spiked with 3,3′,4,4′,5‐pentachlorobiphenyl (PCB 126) and 2,2′,4,4′,5,5′‐hexachlorobiphenyl (PCB 153) such that the diet contained an average of 23, 99, or 561 pg of 2,3,7,8‐tetra‐chlorodibenzo‐p‐dioxin equivalents per gram offish for 21 d. Sixteen additional common tern chicks were similarly dosed with polyhalogenated diaromatic hydrocarbons but were not subjected to the CBT procedure. In weeks 1 and 2, caffeine N‐demethylation and ethoxyresorufin‐O‐deethylation activity on day 21 were elevated in birds that received the greatest PCB dose. There was less constitutive and greater induction of ethoxyresorufin‐O‐deethylation activity than caffeine N‐demethylation. The 14C‐CBT was less invasive than the ethoxyresorufin‐O‐deethylase assay. Only one morphological parameter differed significantly between CBT subjects and no‐CBT subjects fed the same level of PCBs. Bursa weight was significantly less in control CBT subjects than in control no‐CBT subjects, but bursa weights did not differ among CBT and no‐CBT birds from the two PCB treatment groups. No alterations of survival or growth occurred in CBT subjects compared with no‐CBT subjects.