In vivo quantification of oxygen-free radical release in experimental pancreas transplantation

Reactive oxygen species (ROS) were drawn to the attention in the setting of organ transplantation when the 'injury hypothesis' postulated a link between oxidative stress and the activation of the innate immunity of the recipient. While the occurrence of ROS during organ transplantation is undoubted, their onset and magnitude remain largely unknown. We therefore measured ROS using a novel cyclic hydroxylamine spin probe CMH (1-hydroxy-3- methoxycarbonyl-2,2,5,5-tetramethylpyrrolidine) during syngeneic experimental pancreas transplantation in rats in vivo. Organs were subjected to two different cold preservation methods [University of Wisconsin preservation solution (UW) or normal saline] for 18 h. During the first 90 min of reperfusion, samples were collected and analysed using electron paramagnetic resonance signalling. Isolated blood-free perfused organs (IPO) were used for comparison. Analysis showed that it is feasible to detect ROS using CMH spin probes. While IPO organs displayed a very early ROS release, there was no ROS increase in the UW preserved group compared to NaCl. These findings were in line with conventional markers of organ damage such as serum lactate, glucose, potassium as well as tissue ATP levels. CMH spin probes might become a useful tool for the in vivo animal testing of antioxidative substances in models of solid organ transplantation.