DETECTION OF HYDROXYL AND CARBON-CENTERED RADICALS BY EPR SPECTROSCOPY AFTER ISCHEMIA AND REPERFUSION OF THE RAT-KIDNEY

Recent studies suggest that oxygen-derived free radicals are involved in mediating renal reperfusion injury. EPR spectroscopy and spin trapp ing with the spin traps DMPO and PEN, were used to detect and quantita te the formation of hydroxyl radicals in rat kidney after ischaemia-re perfusion in vivo and in vitro in the isolated rat kidney perfused in the absence of leucocytes. EPR analysis of homogenised kidneys and of venous samples did not detect radical adducts with either spin trap. W ith PEN, radical adducts were not detected in vitro. When DMPO was use d as the spin trap in kidneys perfused without albumin in the perfusat e, EPR signals characteristic of hydroxyl and carbon-centred radical a dducts were detected during early reperfusion following ischaemia. The se studies confirm the generation of hydroxyl radicals during ischaemi a-reperfusion in kidney. During reperfusion the total DMPO adduct conc entration reached 4.35 +/- 1.05 nmol/g kidney/3 min, p < 0.05. In cont rol kidneys total adduct were present at lower concentration (2.55 +/- 1.1 nmol/g kidney/3 min). Addition of 15 mM dimethylthiourea abolishe d formation of these adducts following ischaemia-reperfusion but did n ot prevent a reduction in glomerular filtration rate. These results in dicate that significant levels of hydroxyl and carbon-centred radicals are formed in the absence of circulating neutrophils during early ren al reperfusion following ischaemia.