Developmental changes in 7-ethoxyresorufin-O-deethylase (EROD) and delta-aminolevulinic acid dehydratase (ALA-D) activities in three passerines.

In this study, we report changes in 7-ethoxyresorufin-O-deethylase (EROD) and delta-aminolevulinic acid dehydratase (ALA-D) enzyme activities during development of three wild passerine bird species: pied flycather (Ficedula hypoleuca), great tit (Parus major) and blue tit (P. caeruleus). Activities were determined from late embryos, newly hatched, 1-week-old and 15-day-old nestlings and adult birds. EROD activity from hepatic microsomes and ALA-D activity from liver tissue and erythrocytes were measured. In all species investigated EROD and ALA-D activities were increased during the first posthatching week and decreased thereafter. Also, differences between activities in late-term nestlings and adults were seen. Based on these results, we suggest that the developmental status of an animal must always be taken into account when evaluating the results obtained in the biomarker studies.