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

Cytochrome P4501A (CYP1A) activity is often used as a biomarker of exposure of wildlife to polyhalogenated diaromatic hydrocarbons and is usually meas ured ex vivo in liver tissue. A caffeine breath tear (CBT) with radiolabele d substrate (C-14-caffeine) was used to measure in vivo CYP1A activity twic e during development in 14 common tern (Sterna hirundo) chicks treated with polyhalogenated diaromatic hydrocarbons. Tern hatchlings were fed fish spi ked with 3,3',4,4',5-pentachlorobiphenyl (PCB 126) and 2,2',4,4',5.5'-hexac hlorobiphenyl (PCB 153) such that the diet contained an average of 23, 99, or 561 pg of 2,3,7,8-tetrachlorodibenzo-p-dioxin equivalents per gram of fi sh for 21 d. Sixteen additional common tern chicks were similarly dosed wit h 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 eth oxyresorufin-O-deethylation activity than caffeine N-demethylation. The C-1 4-CBT was less invasive than the ethoxyresorufin-O-deethylase assay. Only o ne 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 wei ghts did not differ among CBT and no-CBT birds from the two PCB treatment g roups. No alterations of survival or growth occurred in CBT subjects compar ed with no-CBT subjects.