Mark Wefers Bettink

Chapter 5 88 mitoPO 2 . In the LPS group endotoxemia was induced by intravenous LPS injection (4.5 mg/kg lipopolysaccharide from E.Coli 0127:B8, Sigma-Aldrich, St. Louis, MO, USA). After recording baseline values (T0), a solution of 1 mg/ml LPS was infused during 30 min. Fluid resuscitation was performed by doubling the maintenance colloid infusion directly after LPS application. The timeline of this experiment is shown in figure 1A. Experiment B; Without muscle measurement The 40 rats were randomly divided into 5 groups (8 rats / group); two control groups consisting of a time control group (TC) and a control group receiving methyl-succinate (SC). Three LPS-induced endotoxemic groups consisting of a group in which only LPS was given (LPS --), a LPS group receiving fluid resuscitation (LPS+-), and a LPS group receiving fluid resuscitation and methyl- succinate (LPS++). Fluid resuscitation (Voluven ® , 5 ml*kg -1 *h -1 ) was given to prevent hemodynamic shock and a decline in mitoPO 2 . Succinate dimethyl ester (Brunschwig Chemie, Amsterdam, the Netherlands) was infused (concentration 0.67 M, rate 5 ml*kg -1 *h -1 ) 2h prior to the LPS infusion in the SC and LPS ++ groups. For the remaining groups, the succinate solution was exchanged for saline at the same rate. In all three LPS groups endotoxemia was induced by intravenous LPS injection (3mg/ kg lipopolysaccharide from E.Coli 0127:B8, Sigma-Aldrich, St. Louis, MO, USA). After recording baseline values (T0), a solution of 1 mg/ml LPS was infused during 15 min. Fluid resuscitation was performed by doubling the maintenance colloid infusion directly after LPS application and by an additional fluid bolus of 1 ml during 10 min prior to T1. The timeline of the experiment is shown in Figure 1B. Principle of MitoPO 2 and oxygen disappearance measurements The background of the PpIX-TSLT is described in detail elsewhere (Mik et al., 2008; 2006). In short, PpIX is the final precursor of heme in the heme biosynthetic pathway. PpIX is synthesized in the mitochondria, ALA is the rate-limiting step in this pathway and therefore administration enhances the PpIX concentration substantially. PpIX possesses a triplet state that reacts strongly with oxygen, making its delayed fluorescence lifetime oxygen-dependent according to the Stern-Volmer equation (Mik et al., 2002).