Objectives: To design and establish a model to examine whether brief periods of renal artery occlusion (ischaemic preconditioning, IP) confers protection from the effects of a subsequent period of ischaemia and reperfusion of the rat kidney.
Materials and methods: Ninety rats were randomized into six groups, i.e. sham-operated controls; IP alone; a 20 or 40 min period of left renal ischaemia (RI) alone; and IP followed by a 20 or 40 min period of RI. Preconditioning involved the sequential clamping of the left renal artery for 4 min and its release for 11 min, a total of four times, a 'critical interval' of 30 min before the ischaemic insult. Left renal tissue integrity was determined by dimercapto-succinic acid (DMSA) radionuclide imaging on a gamma-camera both immediately (day 0) and 2 and 9 days later. Acute tubular necrosis was also assessed histologically.
Results: RI for 20 min resulted in a significant decrease in left renal tissue integrity on day 2 only (P < 0.001), whereas RI for 40 min caused significant left renal dysfunction on day 0, day 2 and day 9 (P < or = 0.01). For a given duration of ischaemia, there was no significant difference between results from (IP + RI) rats compared with RI-only rats at any of the three times. There was no significant alteration in renal tissue integrity in the IP-only rats compared with sham-operated controls. Histological findings paralleled the data obtained from DMSA uptake.
Conclusions: The IP regimen and 30 min 'critical interval' confers no protection to the kidney from a 20 or 40 min ischaemic episode. The IP regimen itself appears to have no effect, confirming the validity of our experimental model.