INTERSPECIES DIFFERENCES IN MIXED-FUNCTION OXIDASE ACTIVITY IN BIRDS - RELATIONSHIP BETWEEN FEEDING-HABITS, DETOXICATION ACTIVITIES AND ORGANOCHLORINE ACCUMULATION

The relationship between feeding habits:and interspecies differences i n the detoxication ability of the mixed function oxidase (MFO) system was investigated in birds. The role of MFO (particularly aldrin epoxid ase activity) in the detoxication/bioaccumulation of:organochlorines w as also investigated. Euriphagic (yellow-legged herring gull (Larus ca chinnans), black-headed gull (Larus ridibundus), jackdaw (Corvus moned ula), magpie (Pica pica) and stenophagic (cormorant (Phalacrocorax car bo), coot (Fulica atra) and sparrow (Passer italiae)) species were col lected in northern and central Italy. The following liver microsomal m onooxygenase activities were measured: aldrin epoxidase, ethoxyresoruf in dealkylation (EROD), benzyloxyresorufin dealkylation (BROD) and pen toxyresorufin dealkylation (PROD). NADPH- and NADH-cytochrome c reduct ase (NAD(P)H-CYT-CRED) and NADH-ferricyanide reductase (NADH-FERRIRED) activities were also measured in the liver microsomal fraction. Gluta thione concentration (GSH) was measured in the liver cytosolic fractio n. As a marker of liver damage gamma-glutamyl transpeptidase (GGTP) ac tivity was assayed in the serum. The residues of organochlorines (HCB, pp'DDTs and PCBs) were determined in muscle samples. Omnivorous speci es, particularly the yellow-legged herring gull, had the highest aldri n epoxidase activities. In the yellow-legged hel ring gull the activit y was approximately twice as high as in the jackdaw (p <0.05), black-h eaded gull (p <0.05) and coot (p <0.05). Values five times lower were detected in the specialist fish-eater, the cormorant (p <0.001). The l owest values of aldrin epoxidase activity were detected in the sparrow . Feeding habits were found to be related to evolutionary interspecies differences in MFO activity. A significant statistical correlation (r = 0.656) was found between the 'omnivore index' and MFO detoxication activity expressed as aldrin epoxidation. Organochlorines, and particu larly PCBs, were higher in cormorants and yellow-legged herring gulls from a polluted lagoon than in the other species analysed (black-heade d gull p <0.01; sparrow p <0.001; jackdaw p <0.01; coot p <0.001). Lev els of pp'DDE were much higher in the cormorant and span ow than in th e other birds. Knowledge of the different species-specific detoxicatio n abilities was found to be a useful tool for the identification of sp ecies potentially at risk in environments with high pollution by chlor inated hydrocarbons, or in general contaminants metabolized by the MFO system.