Fig 1. Experimental setting.

Upper panel, schematic diagram of the isolated perfused intestine model. Using a custom made, heated chamber (1) an isolated small intestine (2) is perfused (vascular system: red; luminal system: yellow) while placed on a build-in microbalance (3). A moveable cannulating block (4) carries the tubings, heat exchanger cannula holders (5), and bubble trap (6). Height-adjustable reservoirs (7,8) allow clamping both afterloads to zero. For online analysis of fluid homeostasis all emanating liquids are quantified by use of three balances (9 to 11). Constant flow perfusion is applied by a syringe pump (12) and roller pump (13). The vascular perfusate is prewarmed, oxygenated, and pH equilibrated with tempered hollow fiber dialyzer flushed with carbogen gas (14). Pressure transducer (15–17) allow online detection of the luminal (yellow), venous (blue) and arterial (red) pressures. All data are recorded on a personal computer (18). To secure constant temperature, the chamber and cannulating block are water-jacketed and warmed by water bath (19). The inset shows a representative photograph of a perfused small intestine. A, arterial cannula; B, venous cannula; C, oral intestinal lumen cannula; D, aboral intestinal lumen cannula; E, lymphatic suction needle. Lower panel, experimental setup with treatment groups. In-vivo and ex-vivo ischemic conditioning were performed by inducing no flow ischemic conditions. In-vivo: Three reversible occlusions of the mesenteric artery using a vascular clamp for 5 min followed by 5 min of reperfusion before isolation of the small intestine. Ex-vivo: Interruption of the vascular perfusion by turning off the pumping system of the perfusion chamber for 5 min followed by 5 min of reperfusion repeated for three times. Ex-vivo ischemia/reperfusion damage was induced by replacing O₂ in the perfusion buffer by N₂/CO₂ for a total time period of 60 minutes. Flow was kept constant during that period so that physiological parameters could be analyzed. Replacing O₂ in the perfusion buffer by N₂/CO₂ results in a reduction of pO₂ from initially >600mmHg to values <60mmHg. Since there are no oxygen carriers in the perfusion buffer, this value is equivalent to severe hypoxic conditions.