Meeting Abstract

P1.161  Sunday, Jan. 4  Effects of hyperoxia and intubation of spiracles on oxidative stress in pupae of the moth Antheraea polyphemus. KAISER, A.*; LACAZE, M.; WALKER, A.; Midwestern University, Glendale, AZ; Midwestern University, Glendale, AZ; Midwestern University, Glendale, AZ akaise@midwestern.edu

It has been hypothesized that the air-filled tracheal system of insects has such a high capacity for gas exchange that oxygen supply at rest has to be shut down to prevent excessive oxidative stress. Therefore, insects possess spiracular valves, which control gas exchange between atmosphere and tracheal system. When the spiracles are closed, insects consume oxygen from the tracheal space, reducing intratracheal oxygen partial pressure (PO₂) and perhaps oxidative stress. In this study, we tried to assess the antioxidative function of spiracular control in moth pupae. In one group of animals, we intubated the first three pairs of abdominal spiracles, forcing them to remain constantly open. For 24 hours, we exposed untreated and intubated pupae to either 21% O₂ (normoxia) or 40% O₂ (hyperoxia). We measured CO₂ release rate to control for changes in metabolism and spiracular function. Pupae revealed cyclic, but not discontinuous CO₂ release. After exposure we separated the pupae in three sections: front (head, pro- and meso-thorax), center (meta-thorax and part of abdomen with intubated spiracles), and rear (mobile part of abdomen with untreated spiracles). We measured H₂O₂ production (radical production), total antioxidant capacity, and protein carbonyl concentration (oxidative damage) in the three parts. Neither intubation nor exposure to hyperoxia had a significant effect on any of the parameters between treatment groups. There was, however, a significantly smaller concentration of H₂O₂ and antioxidant capacity in the frontal section compared to the other sections. We suggest that there are either morphological or biochemical differences between frontal section and the rest of the body. We also suggest that 24h blocking of spiracular closure is either not a significant oxidative stressor for with cyclic rather than discontinuous CO₂ release or that oxygen supply is reduced by other mechanisms, like water-filled tracheoles.