DISSOCIATION OF STRUCTURE AND FUNCTION AFTER ISCHAEMIA-REPERFUSION INJURY IN THE ISOLATED PERFUSED RAT KIDNEYS

Abstract

Oxygen-derived free radical* (OFR) involvement in ischacmia-rcpcrfusion (IR) injury was investigated in a rat isolated kidney model, using 20 minutes iscliaemia followed by 15 or 60 minutes reperfusion. Two antioxidants, the xanthine oxidase inhibitor allopurinol and the hydroxyl radical scavenger dimcthylthiourca (DMTU), were uscit to try and prevent OFR-relatcd damage. Renal function was estimated from the inulin clearance, fractional soiiium excretion and renal vascular resistance, location and extent of tubular damage, and type of cell death (apoptosis vs necrosis) were used as morphological parameters of IR-iiuluced change. Cell damage was most extensive in the nephron segments of the outer zone of the outer medulla (straight proximal tubule and thick ascending limb (TAL)). I're-treatment with allopttrinol or DMTU did not Improve renal function. Less structural damage was observed in the TAL of allopuriol - or DMTU - treated kidneys compared with IR alone. In allopurinol - treated kidneys, luminal debris was less extensive than that seen in IR kidneys. Most cell death was necrotic in type and morphological features of apoptosis were seen infrequently. Tlic beneficial effects of allopurinol and DMTU on structural change did not correlate with functional improvement during the reperfusion period, litis may require longer repcrfusion or multiple treatments. Tlie results suggest that OFR ■ injury is of limited significance in this model of renal IR injury. Targeting OFR injury may only be useful after very brief periods of iscliaemia where necrosis is minimal ami the potential for recover}- is greater, Tiie results confirm the different susccptibilitcs of individual nephron segments to injury within the intact kidney. Understanding the molecular response to injury in each segment should facilitate development of methods to accelerate repair after [R injury.