Insect anti-stress responses, including those induced by insecticides, are controlled by adipokinetic hormones (AKHs). We examined the physiological consequences of Pyrap-AKH application on Tribolium castaneum adults (AKH-normal and AKH-deficient prepared by the RNAi technique) treated by two insecticides, pirimiphos-methyl and deltamethrin. Co-application of pirimiphos-methyl and/or deltamethrin with AKH significantly increased beetle mortality compared with application of the insecticides alone. This co-treatment was accompanied by substantial stimulation of general metabolism, as monitored by carbon dioxide production. Further, the insecticide treatment alone affected some basic markers of oxidative stress: it lowered total antioxidative capacity as well as the activity of superoxide dismutase in the beetle body; in addition, it enhanced the activity of catalase and glutathione-S-transferase. However, these discrepancies in oxidative stress markers were eliminated/reduced by co-application with Pyrap-AKH. We suggest that the elevation of metabolism, which is probably accompanied with faster turnover of toxins, might be responsible for the higher mortality that results after AKH and insecticide co-application. Changes in oxidative stress markers are probably not included in the mechanisms responsible for increased mortality.

Department of Biology Josip Juraj Strossmayer University of Osijek Ulica cara Hadrijana 8 A 31000 Osijek Croatia

Faculty of Education University of South Bohemia Jeronýmova 10 371 15 České Budějovice Czech Republic

Faculty of Science University of South Bohemia Branišovská 31 370 05 České Budějovice Czech Republic

Institute of Entomology Biology Centre Academy of Sciences Branišovská 31 370 05 České Budějovice Czech Republic

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