Ascorbate and glutathione regulation in hibernating ground squirrels

Ground squirrels withstand up to 90% reductions in cerebral blood flow duri ng hibernation as well as rapid reperfusion upon periodic arousals from tor por. Metabolic suppression likely plays a primary adaptive role which allow s hibernating species to tolerate such phenomena. However, several other as pects of hibernation physiology are also consistent with tolerance to drama tic fluctuations in cerebral blood flow, suggesting that multiple neuroprot ective adaptations may work in concert during hibernation. The purpose of t he present work, was to study the dynamics of the low molecular weight anti oxidants, ascorbate and glutathione (GSH), during hibernation. Alterations in concentrations of ascorbate during hibernation and arousal in two specie s of hibernating ground squirrels suggest that it in concentrations of asco rbate during hibernation and arousal in two species of hibernating ground s quirrels suggest that it could play a protective role during hibernation or arousal. Samples were collected during the hibernation season from arctic ground squirrels (AGS: Spermophilus parryii) and 13-lined ground squirrels (TLS; S. tridecemlineatus) during prolonged torpor and in squirrels that di d not hibernate or had not been hibernating for several weeks. We determine d antioxidant levels in plasma, cerebrospinal fluid (CSF), and in frontal c ortex, hippocampus and cerebellum using high-performance liquid chromatogra phy (HPLC). Plasma ascorbate concentrations increased dramatically (3-4-fol d) in both species during hibernation and rapidly returned to prehibernatio n levels upon arousal. By contrast, plasma GSH concentrations fell slightly or remained stable during hibernation. Ascorbate levels in the CSF doubled in hibernating AGS (not determined in TLS), while brain ascorbate content fell slightly (10-15%) in both species. Substantial increases in plasma and CSF ascorbate concentrations suggest that this antioxidant could play a pr otective role during hibernation and reperfusion upon arousal from hibernat ion. (C) 1999 Elsevier Science B.V. All rights reserved.