Effect of Organophosphate and Pyrethroid Insecticides on the Expression of GSTs from Tenebrio molitor Larvae

In the present study we report on the effects of two organophosphate and one pyrethroid insecticides on the total activity and the isoenzymic profile of glutathione S-transferase (GST) in the larvae of the insect Tenebrio molitor.Injection of insecticides into the larval body had little effect on the kinetic properties of the unpurified enzyme of the surviving insects. However, dramatic alterations of the isoenzymic profile 24 h after the treatment were observed. The insecticides were administered by injecting into the abdomen an amount close to the LD50dose of the respective compounds. The isoenzymic profile was analyzed in the surviving individuals by means of chromatofocusing. No significant change in the p I of each isoenzyme was noticed although drastic changes were evident in the activity corresponding to each isoenzyme according to the elution profile. These changes following the injection of each insecticide were different, indicating an independent regulation and differential response of the isoenzymes to the administration of the specific insecticides.