Evaluation and protection of water quality requires an understanding of the effects of contaminants on aquatic biota, with a focus on the processes involved with insecticide and pollutant metabolism. Several biotransformation enzymes are adaptive and induced by environmental chemicals. The best known and most sensitive in responding to chemical exposure are the dependent cytochrome P450 microsomal monooxygenases. P450 enzymes metabolize insecticides resulting either in bioactivation or in detoxification, the latter process being enhanced in many strains with metabolic resistance to insecticides. Cytochrome P450 activity was characterized in third instar larvae of the aquatic midge, Chironomus tentans. Optimal in vitro assay conditions with two different substrates (methoxy and ethoxy resorufin) were determined. The activity was concentrated in the microsomal fraction of whole body homogenates and was NADPH dependent. Comparisons of control and atrazine exposed midges indicated increased cytochrome P450 activity as a result of atrazine exposure. This activity was determine by carbon monoxide difference spectra, and by oxidative transformation of the substrates. The molecular weight of this protein was similar in size (45 KDa) to cytochrome P450 enzymes reported for other insects. Immunochemical studies using a Drosophila melanogaster anti-P450 polyclonal antiserum, further support the cytochrome P450 nature of this inducible protein. Finally, the cytochrome P450 family 4 and 6 gene expression in Chironomus tentans was analyzed in third instar larvae exposed to atrazine.
Species 1: Diptera Chironomidae Chironomus tentans
Keywords: Cytochrome P450, Atrazine
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