P2.113 Thursday, Jan. 5 House sparrows oxidize endogenous fuels differently from fasting-adapted species KHALILIEH, A,I.*; MCCUE, M,D.; PINSHOW, B; Mitrani Dept of Desert Ecol, Jacob Blaustein Inst Desert Research, Ben-Gurion Univ of the Negev, 84990; Dept of Biol Sci, St. Mary’s Univ, San Antonio TX, 78228; Mitrani Dept of Desert Ecol, Jacob Blaustein Inst Desert Research, Ben-Gurion Univ of the Negev, 84990 firstname.lastname@example.org
Many wild birds fast during reproduction, molting, migration, or because of limited food availability. Fasting-adapted species sequentially oxidize endogenous fuels in three phases; post-absorptive phase; protein sparing phase; and lethal phase. We hypothesized that species not adapted to long fasts have truncated, but otherwise similar fasting phases, sequential changes in fuel oxidization, and similar blood metabolite changes, to fasting-adapted species. To test the predictions that 1) fasting birds sequentially oxidize substrates in the order: carbohydrates, lipids, and protein; and 2) changes in blood metabolites reflect changes in metabolic fuels as determined by breath analysis. We analyzed the birds' breath for 13CO2 at regular intervals for 24 h after dosing with labeled glucose, palmitic acid, and glycine; we also analyzed plasma for metabolites that reflect catabolism of these substances. Contrary to prediction 1, we found continuous, parallel oxidation of the fuels that correlate with changes in blood metabolites, and these did not indicate division into discrete phases. The rate of glycine oxidization peaked at 30 min, at 2705±687 mmolmin-1 and was also significantly higher (p<0.001) than all other tracers at all post-dosing intervals. Plasma glucose concentration was lowest at hour 8 (225.5±49.7mg/dl) while plasma β-hydroxybutyrate levels increased 6 fold, to 64.3±5.3 mg/dl at the same time. We conclude that the inability of house sparrows to fast for longer than 24 hours is likely related to their inability to separately use different fuels as do fasting-adapted birds.