Oxygen derived free radicals in renal injury: EPR detection and modulation

Full text: Oxygen-derived free radicals (OFRs) may be initiated by a short period of ischaemia followed by reperfusion. The effect in tissues is then similar to damage initiated by radiation-induced OFRs. OFRs have been implicated as one of the main mediators damage to parenchymal and vessel cells of the kidney in ischaemia-reperfusion injury. One of the OFRs, NO production after reperfusion is a potential method of limiting free radical production as well as modifying local blood flow. In the present study, we report the detection of NO in isolated ischaemia-reperfused rat kidneys, and in their perfusate. Detection of NO relies on the formation of a stable iron (II) complex, namely [Fe(MGD)2NO] (MGD = N-methyl-D-gluaminedithiocarbamate) and its subsequent characterisation with multifrequency electron paramagnetic resonance (EPR) spectroscopy. Experiments have been performed in control ischaemia-reperfused kidneys, and in the presence of the NO synthase inhibitor, N-nitro-arginine methylester or a NO generator, nitoprusside. At this stage of our experiments, reperfusion was studied only in the acute phase (60 minutes or less). Renal function (Na excretion, GFR) was measured for all groups, and a comparison was made between the EPR and function results and renal pathology. Although these novel studies are in their initial and trial stages, we have some evidence that modulating the level of NO after ischaemia-reperfusion does limit the amount of ischaemia-reperfusion induced injury, at least in the acute phase