Avian serum esterases: species and temporal variations and their possible consequences

Abstract

Avian serum esterases are predominantly of the 'B' type (cholinesterases and carboxylesterases) and are inhibited by carbamates and the 'active' oxon forms of organophosphorus pesticides. Selective inhibition of mammalian serum carboxylesterase, a 'B' esterase, has shown that this enzyme may play an important role in detoxication by irreversibly binding, and thus inactivating, anticholinesterase compounds. Studies have shown differences between carnivorous and omnivorous/herbivorous avian species in the level of activity and range of forms of carboxylesterases and cholinesterases in sera. In addition, these enzymes show seasonal, diurnal and developmental variations in activity. This paper will discuss species and temporal variations in avian serum 'B' esterases in relation to their possible influence on pesticide toxicity.