Regeneration of ATP in kidney slices after warm ischemia and hypothermic preservation

Abstract

Abstract The current shortage of cadaveric kidneys may be alleviated to some degree by increasing our capabilities to use less than ideal donor kidneys, such as those from non-heart-beating donors. These kidneys are often exposed to no flow (ischemia) for varying lengths of time. Full utilization of these kidneys may require better methods of organ preservation that could reverse existing ischemic injury. This may conceivably require that, during preservation, energy stores (ATP) lost during warm ischemia be recharged. This would require continuous perfusion. Using a kidney slice model, we investigated the effects of simulated hypothermic machine perfusion with the UW gluconate perfusate on the capability of rabbit kidneys exposed to warm ischemia to regenerate ATP. After 30 min of warm ischemia, ATP content was low (0.2 μmol/g wet weight) but increased to 0.7–0.9 μmol/g wet weight after 24 h of simulated machine perfusion at 4 °C. After an additional 2 h of rewarming (37 °C in oxygenated Krebs Henseleit buffer), the slice ATP content increased to about 1.0 μmol/g wet weight (similar to kidneys not exposed to warm ischemia) when the antioxidants desferrioxamine and N-2-(mercaptopropionyl) glycine were included in the preservation media. Significantly less ATP was present without the antioxidants. After 60 min of warm ischemia, less ATP was regenerated after 24 h of simulated machine perfusion (about 0.4 μmol/g wet weight) than after 30 min of warm ischemia. However, more ATP was regenerated when antioxidants were included in the perfusate (0.4 vs 0.8 μmol/g wet weight). This study shows that ATP can be regenerated in kidneys exposed to warm ischemia by continuous perfusion in the UW gluconate solution. Furthermore, oxygen free radicals appear to cause suppression of ATP regeneration since an iron and a hydroxyl radical scavenger improved ATP formation. The ATP content of kidneys exposed to 60 min of WI was less than after 30 min of warm ischemia, suggesting that better methods of preservation may be needed to improve our capability to utilize kidneys damaged by extensive warm ischemia (> 60 min). This may require the development of new methods and/or perfusates for kidney preservation.