Mixed-function Oxidase and Glutathione S-Transferase Activity in a Susceptible and a Fenitrothion-resistant Strain of Oryzaephilus surinamensis (Coleoptera: Cucujidae)

Subcellular preparations of larval and adult Oryzaephilus surinamensts (L.) were used to study involvement of mixed-function oxidases and glutathione S-transferases in the resistance mechanism of a strain highly resistant to fenitrothion. Cytochrome P450 levels per milligram microsomal protein were 3- and 10-fold greater in resistant larvae and adults, respectively, compared with susceptible insects; corresponding increases for aldrin epoxidase activities were 14- and 50-fold. Increases in glutathione S-transferase activities in the resistant strain were minor compared with those of the susceptible strain. Enhanced levels of mixed-function oxidases may indicate a possible biochemical mechanism for fenitrothion resistance in this strain.