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Abstract
Interahemocoelic injection of L-DOPA and Fe2+ (FeSO ) into the 5th instar Schitocerca gregaria 4 caused oxidative damage to proteins, lipids, and DNA in the form of increased levels of carbonyls, peroxides, strand breaks, respectively. No synergism was observed in protein carbonyls production (as key index) when L-DOPA injection was combined with FeSO . Replacement of Fe2+ 4 (FeSO ) with Fe3+ (FeCl ) in the separate combined injections caused lesser amounts of formed 4 3 protein carbonyls. The obtained data were discussed emphasizing autoxidation and redox- cycling properties of L-DOPA and its prooxidant and antioxidant behaviors, as well as participation of the redox-active metal iron in production of reactive oxygen species. Activities of the antioxidant enzymes superoxide dismutase (SOD), catalase (CAT), glutathione peroxidase (GPx), and glutathione reductase (GR) were elevated over constitutive levels, in response to the injected oxidative stressors L-DOPA and iron ions. The levels of both the constitutive and induced activities of GPx and GR are always higher in whole midgut homogenate than in thoracic muscles; this is not always present in the case of SOD and CAT. The K values of GPx are always much m lower than those of CAT in both thoracic muscles and midgut; indicating higher affinities, i.e. higher efficiency, of the GPx than CAT to the substrate H O The results may represent some sort 2 2. of stressful conditions that may increase the vulnerability of insect pests to control measures