Endothelium-dependent vasodilation in the isolated rabbit kidney following in vivo and in vitro ischaemia and reperfusion: effects of antagonizing platelet activating factor (PAF)

Renal ischaemia-reperfusion (I/R) is a pathological condition occurring frequently after transplantation and acute renal failure. A mediator thought to play a role in the disturbed haemodynamics of I/R is platelet activating factor (PAF). We studied endothelium-dependent (acetylcholine, ACh) and -independent (sodium nitroprusside, SNP) vasorelaxant responses and the effect of BN 52021, a PAF antagonist, in the isolated perfused rabbit kidney after in vivo and in vitro I/R. Anaesthetized rabbits underwent right nephrectomy and 1 h left renal artery clamping followed by 30min reperfusion with blood. In another group, kidneys were isolated and, after transferral to the perfusion system, the perfusion pump was turned off for 1 h, followed by 30min reperfusion with Krebs' solution. BN 52021 or its vehicle dimethylsulphoxide (DMSO) was administered 20min before left renal artery occlusion or turning off the pump. Although in vitro I/R did not influence ACh-induced responses, in vivo I/R caused a decrease which was prevented by BN 52021. SNP-induced responses did not change in in vitro I/R and decreased only at lower concentrations in in vivo I/R, whereby pretreatment with BN 52021 did not offer any protection. It is concluded that in vivo I/R diminishes ACh-induced endothelium-dependent vasodilation, possibly via PAF and blood components, whereas SNP-induced endothelium-independent vasodilation was not altered by in vivo and in vitro ischaemia in the isolated rabbit kidney.