Mark Wefers Bettink

Monitoring mitochondrial respiration 5 87 medetomidine 0.5 mg kg -1 (Sedator, Eurovet Animal Health BV, Bladel, the Netherlands) and atropine 0.05 mg kg -1 (Centrofarm Services BV, Etten-Leur, the Netherlands). Tracheotomy was performed to enable mechanical ventilation. Ventilator settings were adjusted on end-tidal PCO 2 , keeping the arterial CO 2 partial pressure between 35-45 mmHg; the inspired oxygen concentration was set at 40%. The right jugular vein was catheterized with a polyethylene 0.9 mm catheter for intravenous fluid administration. The left femoral artery was catheterized to monitor arterial blood pressure and heart rate, and for hourly blood gas analysis. Cardiac output was measured by a thermodilution method with a thermistor inserted in the right carotid artery. Anesthesia and fluid balance were maintained by continuous infusion of ketamine (50 mg kg - 1 h -1 ), a crystalloid (Ringer’s, B. Braun Melsungen AG, Melsungen, Germany) and a synthetic colloid solution (2.5 mL kg -1 h -1 ) (Voluven ® , Fresenius Kabi, Bad Homburg, Germany). Body temperature was measured rectally and maintained at 38 ± 0.5°C by means of a heating pad. Experimental procedures Abdominal hair was removed by shaving followed by application of commercially available hair removal cream (Veet, Reckitt Benckiser Co., Slough, UK) for about 5 min. PpIX was induced by applying a freshly prepared 2.5% 5-aminolevulinic acid (ALA) (Sigma-Aldrich, St. Louis, MO, USA) in hydrophilic cremor lanette (Lanettecreme I FNA, Bipharma, Weesp, the Netherlands). The skin was covered with aluminum foil to protect PpIX from light exposure. Experiment A; With muscle measurement The skin above the m. quadriceps femoris was removed. The ALA applied on the skin and muscle were covered with an adhesive film to avoid oxygen diffusion from the surroundings. The ALA applied tissue was covered with aluminum foil to protect PpIX from light exposure. The 14 rats were divided into 2 groups; a time-control group (M-TC, N=6) and a LPS- induced endotoxemic group (M-LPS, N=8). TC were matched on duration of the experiment, a lactate concentration above 2 mmol/l in the blood gas analysis was used as a marker for the second ODR measurement in the LPS group. Fluid resuscitation (Voluven®, 5 ml*kg-1*h-1) was given to prevent hemodynamic shock and a decline in