Transmission of high arterial pressure into renal microvessels during venous‐clamping augments ischaemia/reperfusion‐induced acute kidney injury in anaesthetized rats

Abstract Aim In two recent studies, we observed that a 30‐min renal vein clamping caused formation of interstitial haemorrhagic congestion in ischaemic and ischaemic/reperfused kidney along with the development of severer acute kidney injury (AKI) than renal artery or pedicle clamping. It was suggested that the transmission of high arterial pressure into renal microvessels during vein occlusion probably causes the occurrence of interstitial haemorrhagic congestion that augments AKI. The present investigation aimed to evaluate this suggestion by reducing renal perfusion pressure (RPP) during renal venous occlusion. Methods Anaesthetized male Sprague–Dawley rats were divided into three groups ( n = 8), which underwent a 2‐h reperfusion period following 30‐min bilateral renal venous clamping along with reduced RPP (VIR‐rRPP group) or without reduced RPP (VIR group) and an equivalent period after sham‐operation (Sham group). Results The VIR‐rRPP group compared with VIR group had lower levels of kidney malondialdehyde and tissue damages as epithelial injuries of proximal tubule and thick ascending limb, vascular congestion, intratubular cast and oedema, along with the less reductions in renal blood flow, creatinine clearance, Na + ‐reabsorption, K + and urea excretion, urine osmolality and free‐water reabsorption. Importantly, the formation of intensive interstitial haemorrhagic congestion in the VIR group was not observed in the VIR‐rRPP group. Conclusion These results indicate that the transmission of high arterial pressure into renal microvessels during venous occlusion leads to rupturing of their walls and the formation of interstitial haemorrhagic congestion, which has an augmenting impact on ischaemia/reperfusion‐induced renal structural damages and haemodynamic, excretory and urine‐concentrating dysfunctions.