Meeting Abstract
As days shorten and ambient temperature decreases towards winter some temperate-zone mammals develop heterothermy. However, not all individuals respond equally to these changes; photo-responders use daily torpor, while non-responders are normothermic throughout a year. Since responders are potentially subjected to higher oxidative stress resulting from rapid increase in metabolic rate during frequent arousals from torpor, we hypothesized that their antioxidant capacity would be higher than in non-responders. To test the prediction that responders and non-responders differ in oxidative capacity and antioxidant potential, we measured concentration of reactive oxygen metabolites (ROM, mg H2O2 dl-1) and biological antioxidant potential (BAP, μmol vitamin C l-1) using the FRAS4 evolvo system (H&D, Parma, Italy). We used 80 male and 80 female Siberian hamsters (Phodopus sungorus) which were acclimated to summer (16L:8D, 20°C) and then to winter (8L:16D, 10°C). After each acclimation, ROM and BAP were measured in blood drawn from the retro-orbital sinus. We found that responders and non-responders did not differ in the ROM or BAP. However, antioxidant potential increased from summer to winter by ~20% (p<0.001), and it was true for both sexes and phenotypes. Irrespective of season and phenotype, females had lower ROM than males (p<0.05). These results do not support our original hypothesis. It looks however, that Siberian hamsters increase their antioxidant defense in winter. Responders did not differ from non-responders, as both rely on non-shivering thermogenesis to cope with cold when active on the daily basis. The study was supported by the grant #NCN 2014/13/B/NZ8/04698.
