Bandouchova et al. Acta Veterinaria Scandinavica 2011, 53:2 http://www.actavetscand.com/content/53/1/2 Page 10 of 13 Figure 10 Low molecular weight antioxidants oxidizable at a potential of 680 mV (i.e. glutathione) in plasma samples of European brown hares on individual days post-inoculation with F. tularensis. See Figure 1 for a detailed description of groups. compounds is in the range of 1-10 μM. This range of sensitivity is sufficient for determining the physiological concentrations of biologically relevant scavengers. It may be hypothesized that the increase in glutathione levels as a response to oxidative stress conferred by the F. tularensis infection further promotes its multiplica- tion because this antioxidant provides the essential source of cysteine required for the growth and prolifera- tion of Francisella [17]. Reactive nitrogen species (RNS) and reactive oxygen species (ROS) are intermediates that are involved in the host defence against various intracellular pathogens including F. tularensis. The production of reactive mole- cular species is induced in macrophages when they are exposed to pro-inflammatory cytokines, including IFN-g and TNF-a. After activation, macrophages are capable of arresting bacterial replication [39]. F. tularensis is exposed to ROS and RNS not only in macrophages but also in other cell types or extracellularly in vivo, and both F. tularensis tularensis and holarctica subspecies are assumed to be virulent as they are armed with a variety of enzymes that can combat host ROS- and RNS-mediated killing mechanisms [40]. These processes may result in the peroxidation of cellular lipids due to hydroxyl radical production. It is possible to evaluate lipid peroxidation as a measure of oxidative damage. As shown in Figure 11, there was about a two-fold increase in lipid peroxidation assessed as total thiobarbi- turic acid reactive species (TBARS) in the F. tularensis- inoculated group of European brown hares on days 4 to 8 post-inoculation. From day 10, the TBARS level returned to within the normal range, probably due to the protective action of increased antioxidants (cf. Fig- ures 9 and 10). The normal levels of TBARS in healthy European brown hares have not yet been reported. The TBARS of control hares in the present study ranged from 0.81 to 1.54 μmol/l. These values are similar to those found in humans (1.20 ± 0.30 μmol/l) [41]. Statistical analysis revealed a significant correlation between the uric acid levels measured using standard procedures of dry chemistry and LMWAs oxidizable at a potential of 550 mV (represented by the content of uric and ascorbic acids) assayed using square wave vol- tammetry in European brown hares on individual days post-inoculation with F. tularensis as well as in controls from days 0 to 35 (n = 96, R = 0.57, p = 0.01). LMWAs such as uric and ascorbic acids and glutathione were assayed using square wave voltammetry and the results