Efeito oxidante do imidacloprido em abelhas melíferas (Apis mellifera L.) e potencial ação antioxidante da cafeína
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Data
2017-02-20
Autores
Balieira, Kamila Vilas Boas [UNESP]
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Universidade Estadual Paulista (Unesp)
Resumo
Pesticidas são considerados um dos principais fatores do declínio populacional das abelhas e substâncias antioxidantes podem auxiliar na proteção desses insetos contra esses produtos. Foram avaliados o efeito oxidante do imidacloprido em abelhas melíferas (Apis mellifera L.) e a ação antioxidante da cafeína. Foram usadas seis dietas à base de xarope (água e açúcar 1:1), controle (apenas xarope); xarope com adição de 0,1 ng de imidacloprido/abelha; xarope com adição de 0,3 ng de imidacloprido/abelha; xarope com 5 μg/mL de cafeína; xarope com adição de 5 μg/mL cafeína e 0,1 ng de imidacloprido/abelha; xarope com adição de 5 μg/mL cafeína e 0,3 ng de imidacloprido/abelha. Após 72 horas da alimentação, foi preparado homogenato do tórax e avaliados: atividade das enzimas glutationa peroxidase (GPx) e catalase (CAT), concentrações de glutationa reduzida (GSH), glutationa oxidada (GSSG), estado oxidativo dos nucleotídeos de piridina (NAD(P)H) e grupos tióis de proteínas, além da formação de malondialdeído (MDA), um indicador de lipoperoxidação. Foi avaliada a sobrevida média de 360 abelhas recém-emergidas (1°dia), alimentadas com as dietas experimentais até às 72 horas, e o consumo médio da dieta por abelha. O imidacloprido aumentou a atividade da GPx em relação ao controle nas duas doses testadas, apresentando um efeito dose-dependente, e o mesmo foi observado com a cafeína. A adição de cafeína juntamente com 0,3 ng de imidacloprido/abelha, estimulou ainda mais a atividade da enzima. Observou-se também aumento na atividade da CAT pelas duas doses do imidacloprido e pela cafeína em relação ao controle. A adição da cafeína não alterou o efeito das doses do inseticida sobre a CAT. Nenhum dos tratamentos alterou a razão entre as concentrações de GSH e GSSG (GSH/GSSG) ou a concentração de NAD(P)H. Foi observada uma redução significante na concentração de grupo tióis de proteínas em relação ao grupo controle nas abelhas tratadas com as duas doses do imidacloprido, e a adição de cafeína protegeu contra a oxidação desses grupos. Para a concentração de MDA, observou-se aumento dose-dependente do imidacloprido em relação ao controle. A cafeína diminuiu parcialmente esse efeito, indicando que inibiu a lipoperoxidação. A sobrevida média das abelhas durante 72 horas não foi alterada por nenhum dos tratamentos. O consumo das dietas foi maior para as abelhas tratadas com 0,3 ng de imidacloprido/abelha. Os resultados do presente estudo indicam que o imidacloprido provocou danos oxidativos nas abelhas melíferas, enquanto que a cafeína atuou como antioxidante, e ainda, que as abelhas melíferas têm o consumo estimulado quando o alimento estiver intoxicado com o imidacloprido.
Pesticides are the main factors in the population decline of bees and antioxidant substances may aid in protecting these insects against these products. The oxidizing effect of imidacloprid in honey bees (Apis mellifera L.) and the antioxidant action of caffeine were evaluated. Six diets based on syrup (water and sugar 1: 1), control (syrup only) were used; syrup with addition of 0.1 ng imidacloprid/bee; syrup with addition of 0.3 ng imidacloprid/bee; Syrup with 0.5 μg/mL caffeine; syrup with addition of 5 μg/mL caffeine and 0.1 ng imidacloprid/bee; syrup with addition of 5 μg/mL caffeine and 0.3 ng imidacloprid/bee. After 72 hours of use, the activity of glutathione peroxidase (GPx) and catalase (CAT), concentrations of reduced glutathione (GSH), oxidized glutathione (GSSG), oxidative state of pyridine nucleotides (NAD(P)H) and thiol groups of protein, besides the production of malondialdehyde (MDA), an indicator of lipoperoxidation. The longevity of 360 freshly emerged bees (1st day), fed experimental diets, was evaluated. Imidacloprid increased GPx activity compared to the control, in a dose-dependent manner, and the same and was observed with caffeine. The addition of caffeine with 0.3 ng of imidacloprid/bee stimulated the activity of the enzyme. There was an increase in CAT activity by the two doses of imidacloprid in relation to the control and also by caffeine. The addition of caffeine did not alter the effect of doses of the insecticide on the CAT activity. The GSH:GSSG ratio or the NAD(P)H concentration were not affected. A significant reduction in the concentration of thiol group of proteins was observed in the two groups of imidacloprid relative to the control group, and the addition of caffeine protected against the oxidation of these groups. Imidacloprid caused a dose-dependent increase in the MDA concentration while the addition of caffeine partially decreased this effect, indicating that it inhibited the lipoperoxidation. The average survival of the bees during 72 hours was not altered by any of the treatments. Diets consumption was higher for bees treated with 0.3 ng imidacloprid/bee. The results of the present study indicate that imidacloprid caused oxidative damage in honey bees, whereas the caffeine acted as an antioxidant, and also that the consumption is stimulated when the food is intoxicated with imidacloprid.
Pesticides are the main factors in the population decline of bees and antioxidant substances may aid in protecting these insects against these products. The oxidizing effect of imidacloprid in honey bees (Apis mellifera L.) and the antioxidant action of caffeine were evaluated. Six diets based on syrup (water and sugar 1: 1), control (syrup only) were used; syrup with addition of 0.1 ng imidacloprid/bee; syrup with addition of 0.3 ng imidacloprid/bee; Syrup with 0.5 μg/mL caffeine; syrup with addition of 5 μg/mL caffeine and 0.1 ng imidacloprid/bee; syrup with addition of 5 μg/mL caffeine and 0.3 ng imidacloprid/bee. After 72 hours of use, the activity of glutathione peroxidase (GPx) and catalase (CAT), concentrations of reduced glutathione (GSH), oxidized glutathione (GSSG), oxidative state of pyridine nucleotides (NAD(P)H) and thiol groups of protein, besides the production of malondialdehyde (MDA), an indicator of lipoperoxidation. The longevity of 360 freshly emerged bees (1st day), fed experimental diets, was evaluated. Imidacloprid increased GPx activity compared to the control, in a dose-dependent manner, and the same and was observed with caffeine. The addition of caffeine with 0.3 ng of imidacloprid/bee stimulated the activity of the enzyme. There was an increase in CAT activity by the two doses of imidacloprid in relation to the control and also by caffeine. The addition of caffeine did not alter the effect of doses of the insecticide on the CAT activity. The GSH:GSSG ratio or the NAD(P)H concentration were not affected. A significant reduction in the concentration of thiol group of proteins was observed in the two groups of imidacloprid relative to the control group, and the addition of caffeine protected against the oxidation of these groups. Imidacloprid caused a dose-dependent increase in the MDA concentration while the addition of caffeine partially decreased this effect, indicating that it inhibited the lipoperoxidation. The average survival of the bees during 72 hours was not altered by any of the treatments. Diets consumption was higher for bees treated with 0.3 ng imidacloprid/bee. The results of the present study indicate that imidacloprid caused oxidative damage in honey bees, whereas the caffeine acted as an antioxidant, and also that the consumption is stimulated when the food is intoxicated with imidacloprid.
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Palavras-chave
Apicultura, Estresse oxidativo, Inseticidas, Lipoperoxidação