The processes involved in the renal damage resulting from ischemia-reperfusion injury are poorly understood. This study examined the contribution of prostaglandins and nitric oxide (NO) in the vascular responses to ischemia-reperfusion injury in the kidneys of normotensive and hypertensive rats. Groups of Wistar and stroke prone spontaneously hypertensive rats (SHRSP) were dosed with polyethylene glycol vehicle, aspirin (53.5mg/Kg/day), NO-aspirin (100mg/Kg/day) or celecoxib (10mg/Kg/day) for 7 days. On day 7 rats were anesthetized with chloralose/ urethane and the left kidney was exposed to a 30-min period of ischemia followed by 90-min reperfusion. Renal cortical and medullary perfusions were monitored throughout using laser-Doppler flowmetry. In the vehicle and celecoxib treated Wistar rats, cortical and medullary post-ischemia perfusion was reduced to 66% and 62% and 53% and 62%, respectively (all P<0.05) of baseline. The ischemia induced reductions in cortical and medullary flux were ameliorated in the aspirin and NO-aspirin groups where flux fell to 96% and 78% and105% and 83% respectively (P<0.05). There was a fall in cortical and medullary flux in the post-ischemic period in the vehicle treated SHRSP to 82% and 77% (P<0.05). These findings show that non-selective COX inhibition, and to an even greater extent NO donation, provided protection to the renal vasculature from ischemic injury in the Wistar rat but not in the SHRSP. This would suggest that prostaglandins are less important in the development of renal ischemia-reperfusion injury during hypertension and both COX isoforms must be inhibited to offset the decrease in renal hemodynamics.