Atrazine induction of cytochrome P450 in Chironomus tentans larvae

Cytochrome P450-dependent aldrin epoxidation was characterized in third ins tar larvae of the aquatic midge, Chironomus tentans. Optimal in vitro assay conditions for the epoxidase were pH 7.6 and 31 degrees C. Activity was li near up to 40 min of incubation time and 0.5 mg microsomal protein per incu bation. The activity was concentrated in the microsomal fraction of whole b ody homogenates and was NADPH-dependent, The effect of atrazine exposure on aldrin epoxidase was measured to determine if this herbicide induces cytoc hrome P450-dependent activity. Comparisons of control and atrazine-exposed midges indicated increased epoxidase activity as a result of atrazine expos ure, and a 45 kDa protein of increased intensity was observed after SDS-PAG E of microsomal protein. The molecular weight of this protein was similar i n size to cytochrome P450 enzymes reported for other insects. Heme staining of SDS-PAGE gels and immunochemical studies using a Drosophila melanogaste r anti-P450 polyclonal antiserum, further support the cytochrome P450 natur e of this inducible 45 kDa protein. (C) 1999 Elsevier Science Ltd. All righ ts reserved.