Modulation of mixed-function oxidase activity in Black-headed gulls living in anthropic environments: biochemical acclimatization or adaptation?

This study was conducted to explore the role of the mixed-function oxidase (MFO) detoxication system in the "biochemical acclimatization" or adaptation of gulls to anthropic environments. In three different populations of black-headed gull (Larus ridibundus) feeding in a lagoon, in municipal and industrial landfills, MFO microsomal hepatic activities (aldrin epoxidase, 7-ethoxyresorufin-O-deethylase, NADPH-cytochrome c reductase, NADH-cytochrome c reductase, and NADH-ferricyanide reductase), microsomal alpha-naphthylacetate esterase activity, cytochrome P-450 forms, and chlorinated hydrocarbon residues were determined. Induction tests and in vitro comparative kinetics studies were completed between the different populations of gulls. The detoxicant activities of the MFO system were much higher in the landfill gulls, especially those of the industrial landfill, than in lagoon gulls. Lineweaver-Burk plots for aldrin epoxidase show an apparent K(m) four to five times lower in the gulls of the industrial landfill than in the other two populations. The origin of the potentiated detoxication activities in landfill gulls is investigated and the hypotheses of biochemical acclimatization and genetic adaptation are discussed.