DNA FRAGMENTATION REDUCED BY ANTIOXIDANTS FOLLOWING ISCHEMIA-REPERFUSION IN THE ISOLATED-PERFUSED RAT-KIDNEY

The role of oxygen-derived free radicals (OFR) in modifying structure and function after ischaemia-reperfusion (IR) injury was studied in is olated perfused rat kidneys (IPRK). Control kidneys were studied after 20 min of ischaemia followed by 15 or 60 min of reperfusion. The xant hine oxidase inhibitor allopurinol and the hydroxyl radical scavenger dimethylthiourea (DMTU) were used to prevent OFR-related damage. Morph ological injury was assessed in cortex, inner and outer medulla and co mpared with indices of global renal function (inulin clearance, fracti onal sodium excretion and renal vascular resistance). Apoptosis was as sessed using both morphological criteria and in situ end-labelling (IS EL) to identify DNA fragmentation. Tubular damage, as evidenced by cel lular blebbing, tubular cast formation, epithelial necrosis, and occas ional apoptosis, was greatest in the straight proximal tubule and thic k ascending limb (TAL) in the outer zone of the outer medulla. Pretrea tment with allopurinol or DMTU did not significantly improve renal fun ction. However, structural damage and luminal debris were diminished i n allopurinol- and DMTU-treated kidneys. These changes may lead to fun ctional improvement after more prolonged reperfusion. In situ end-labe lling was more frequent in distal tubular epithelial cells after IR th an either morphological evidence of apoptosis or necrosis. Decreased I SEL was observed after pretreatment with both allopurinol and DMTU. Th e data demonstrate that OFR produce DNA damage after IR, increasing IS EL. This probably represents reversible DNA damage rather than incipie nt apoptosis. Thus, antioxidants reduce or prevent DNA and cellular in jury after IR and may reduce functional impairment after prolonged rep erfusion.