Reduction in nonparenchymal cell injury and vascular endothelial dysfunction after cold preservation of the liver by gaseous oxygen

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Abstract
Reintroduction of oxygen to previously anoxic tissue may result in severe cell injury (oxygen paradox) and contribute to the so-called reperfusion damage of ischemic organs. Our study investigated the influence of simple gaseous oxygen supply during ischemia on nonparenchymal cell alterations upon reperfusion of the liver. Livers from male Wistar rats were isolated, rinsed blood-free and stored for 48 h at 4 degrees C in UW-preservation solution (group 1; n = 6). Gaseous oxygen was insufflated into a second group of livers (group 2; n = 6) during the storage period via the inferior caval vein at a pressure limited to 18 mmHg. To simulate the period of slow rewarming of the organ during surgical implantation in vivo, all livers were incubated at 25 degrees C in saline solution for 30 min prior to reperfusion. Reperfusion was carried out in vitro in a recirculating system with Krebs-Henseleit buffer. A control group was perfused immediately after harvest. The technique of aerobic storage (group 2) resulted in normal vascular perfusion characteristics without elevation of portal venous pressure (PVP) above control values, in contrast to group 1 livers which showed a significantly elevated PVP, averaging between 1.5 and 2 times the values of the control. Hepatic efflux of NO (nmol/ml) after 10 min of reperfusion was massively increased in group 1, while only low concentrations were found in group 2 and in control livers. Kupffer cell activation after ischemia was shown by a huge increase in acid phosphate release upon reperfusion compared with the control, with significantly lower values in group 2 after 10 min of reperfusion than in group 1. Thus, aerobic ischemia by gaseous oxygen persufflation seems an appropriate tool for long-term organ preservation, preventing vascular and parenchymal dysfunction upon reperfusion.