Ascorbate dynamics and oxygen consumption during arousal from hibernation in Arctic ground squirrels

During hibernation in Arctic ground squirrels (Spermophilus parryii), O-2 c onsumption and plasma leukocyte counts decrease by >90%, whereas plasma con centrations of the antioxidant ascorbate increase fourfold. During rewarmin g, O-2 consumption increases profoundly and plasma ascorbate and leukocyte counts return to normal. Here we investigated the dynamic interrelationship s among these changes. Plasma ascorbate and uric acid (urate) concentration s were determined by HPLC from blood samples collected at similar to 15min intervals via arterial catheter; leukocyte count and hematocrit were also d etermined. Body temperature, O-2 consumption, and electromyographic activit y were recorded continuously. Ascorbate, urate, and glutathione contents in body and brain samples were determined during hibernation and after arousa l. During rewarming, the maximum rate of plasma ascorbate decrease occurred at the time of peak O-2 consumption and peak plasma urate production. The ascorbate decrease did not correlate with mouth or abdominal temperature; u ptake into leukocytes could account for only a small percentage. By contras t, liver and spleen ascorbate levels increased significantly after arousal, which could more than account for ascorbate clearance from plasma. Brain a scorbate levels remained constant. These data suggest that elevated concent rations of ascorbate {[ Asc]} in plasma {[ Asc](p)} provide an antioxidant source that is redistributed to tissues during the metabolic stress that ac companies arousal.