|
(19-39) Additive effects of a pesticide (dimethoate) and heavy metals on metabolic responses in a grasshopper (Chorthippus brunneus) from a heavy metals pollution gradient. Augustyniak, Maria*,1, Migula, Pawel1, Babczynska, Agnieszka1, Kafel, Alina1, Wilczek, Grazyna1, 1 University of Silesia, Katowice, Poland ABSTRACT- Our previous studied showed that defensive strategy of Ch. Brunneus from five meadow sites localised along a metal polluted gradient in southern Poland (from 10,000 to 150 mg Zn kg-1 of humus) include better avoidance mechanisms, confirmed by positively correlated activity a series of detoxifying enzymes with heavy metal levels in their diet. In this study we checked how an exposure to additional stressing factor (organophosphorous pesticide dimethoate used in a concentration of 0.32 Key words: Chorthippus brunneus , dimethoate, heavy metals, detoxifying enzymes |
g/individual) might affect detoxifying abilities of grasshoppers collected at the same meadow sites as in the former studies. Assays were carried out 24 hrs after topical treatment. Inhibition of AChE, used here as a specific biomarker of exposure, reached nearly 50%, without significant differences between experimental groups, which differed in relation to the pre-exposure with heavy metals. The pesticide caused also a significant decrease in glutathione S-transferase and glutathione peroxidases activities and glutathione levels (GSSG+GSH) in grasshoppers from all selected groups, demonstrating a high sensitivity of glutathione-dependent metabolism to the additional stressing factor. Also in the case of glutathione reductase (GR) and carboxylesterases the fall of activity was shown for all groups, except for the insects from the most polluted area where a high level of GR activity was maintained, suggesting a repeated use of this tripeptide in situation of exceptionally low glutathione levels stated in these grasshoppers, which is energetically less expensive. This might be one of the trade-off mechanisms adapting them to life the seriously polluted environment.