Reactive oxygen species (ROS) can profoundly impact tissues and are the basis for the oxidative stress theory of aging. ROS generation may be the greatest in metabolically active tissue, such as exercising muscle, and may preferentially damage mitochondria, the major site of ROS formation. However, few studies have examined exercise induced mitochondrial damage and none have done so over the course of an animal's life. Flying honey bees produce the highest mass-specific metabolic rate measured; suggesting their flight muscles and mitochondria may experience high levels of oxidative stress during normal activities. To address this, I assessed markers of oxidative stress in forager and nurse honey bee mitochondria isolated from flight muscle in "Young" (9 -10 days post adult emergence), "Old A" (19-20 days post adult emergence), and "Old B" (24-25 days) individuals. All collections were made from single-cohort colonies (SCC) that allow for the comparisons of flight induced oxidative stress between age-matched foragers and nurses as well as different aged foragers performing the same task. Foragers had been actively foraging for either 1-3 days (Young and Old B) or >12 days (Old A) prior to collection. To assess oxidative capacity and mitochondrial oxidative stress, I measured enzymatic levels of the citrate synthase (an indicator of oxidative capacity) and aconitase (to measure ROS damage) from the citric acid cycle. I also measured hydrogen peroxide production (an indicator of ROS formation), and lipid peroxidation (to measure ROS damage) from isolated flight muscle mitochondria. Citrate synthase levels were similar regardless of age, activity, or behavior group with an average of 268.1 ± 28.4 μmol TNB min-1mg protein -1 for foragers and an average of 245.2 ± 29.7μmol TNB min -1mg protein -1 for nurses suggesting similar levels of oxidative capacity in all groups. In addition, I did not find an age or activity related decline in aconitase activity as forager and nurse bees aged. Foragers "Old B" with low flight history had a reduced amount of aconitase activity with an average of 0.99 ± 0.98 μmol NADH min -1μg protein -1. This data suggests that either repeated forager flight does not subject bees to oxidative stress and/or aconitase is not a definitive measure of oxidative stress in this species (Sohal, 2002).Contrary to what was predicted, H2O2 production was the lowest in "Old A" foragers with high flight history (>12 days of foraging behavior) with an average of 0.26 ± 0.01 μmol H2O2 min -1ng protein -1 approximately a 30% decrease compared to both the "Young" and "Old B" foragers. While, H2O2 production was similar in all nurse groups with an average of 0.403 ± 0.03 μmol H2O2 min -1ng protein -1. The forager "Old B" group had the highest level of lipid peroxidation with an average of 0.66 ± 0.04 μmol MDA min-1μg protein -1. The nurse groups "Old A" and "Old B" had similar levels of lipid damage with an average of 0.43 ± 0.02 μmol MDA min-1μg protein -1. There was a reduced level of lipid oxidation in the "young" nurse group with an average of 0.24 ± 0.06 μmol MDA min-1μg protein -1. Taken together our data indicates that ROS formation and lipid peroxidation in foragers with the most flight history may be reduced behaviorally by carrying lighter/lesser loads, less foraging trips, or flying shorter distances. Another possibility is the use of uncoupling proteins as a mechanism of protection for the metabolically active foragers with high flight history. In summary, I did not find the predictive levels of oxidative stress in old foragers with high flight history, however life long flight activity demonstrated potential mechanisms of behaviorally reducing ROS formation or uncoupling proteins to serve as a mechanism of protection from flight induced ROS formation.
|Commitee:||Jennings, David, Luesse, Darron|
|School:||Southern Illinois University at Edwardsville|
|School Location:||United States -- Illinois|
|Source:||MAI 53/01M(E), Masters Abstracts International|
|Keywords:||Aging, Honey bee, Oxidative stress|
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