EFFECTS OF POLYHALOGENATED AROMATIC-HYDROCARBONS (PHAHS) ON BIOCHEMICAL PARAMETERS IN CHICKS OF THE COMMON TERN (STERNA-HIRUNDO)

Common tern (Sterna hirundo) eggs were collected from eight breeding c olonies that differed in degree of polyhalogenated aromatic hydrocarbo n (PHAH) pollution. The eggs were artificially incubated and the chick s sacrificed within 12 hours after hatching. Plasma thyroid hormones ( total thyroxine (TT4), free thyroxine (FT4) and triiodothyronine (TT3) ), hepatic T4-glucuronyltransferase (T4-UGT) activity, plasma retinol and yolksac retinoid levels were measured and compared with yolksac PH AH residues and hepatic ethoxyresorufin- and pentoxyresorufin-O-deethy lase (EROD and PROD) activities. The yolksac PHAH residues measured we re polychlorinated biphenyl (PCB), polychlorinated dibenzofuran (PCDF) and polychlorinated dibenzo-p-dioxin (PCDD). No significant differenc es were observed between colony average levels of plasma thyroid hormo nes (TT4, FT4 and TT3) nor plasma retinol levels and T4-UGT activities that could be related to colony average PHAH levels. However, average colony yolksac retinyl ester levels did show significant differences. When correlated for individual terns, significant correlations betwee n all these parameters and PHAH levels or EROD or PROD activities were found. The correlation between hepatic T4-UGT and EROD and PROD activ ities was very strong, suggesting a concomitant induction of these dru g metabolizing enzymes. The PHAH levels were expressed as dioxin equiv alents (TEQs) based on toxic equivalence factors (TEFs) as proposed by Safe (1990, 1994). In addition to plasma retinol, another retinoid wa s found which resembles 3,4-didehydro-retinol (vitamin A2) in chromato graphic and spectroscopic behaviour. This putative plasma vitamin A2 w as significantly positive correlated with the yolksac TEQs and with th e hepatic EROD activity. Esters of both retinol and putative vitamin A 2 were detected in the yolksac. The average yolksac vitamin A2 levels of the cleanest Zeewolde colony were significantly higher than the ave rage levels in the other colonies. It was not possible to correlate th e yolksac retinoids with residue levels or TEQs for individual terns, as these had not been analyzed in the same yolksacs. Common tern chick s that required a longer period of incubation before hatching had sign ificantly lower levels of yolksac retinyl palmitate and higher PHAH le vels. The ratio plasma retinol over yolksac retinyl palmitate was sign ificantly increased.