The kidney during hibernation and arousal from hibernation. A natural model of organ preservation during cold ischaemia and reperfusion

Background. During hibernation the kidney is in a hypothermic condition whe re renal blood flow is minimal and urine production is much reduced. Period ical arousal from hibernation is associated with kidney reperfusion at incr easing body temperature, and restored urine production rate. Methods. To assess the degree of structural preservation during such extrem e conditions, the kidney cortex was investigated by means of electron micro scopy in the dormouse Muscardinus avellanarius during winter hibernation, a rousal from hibernation and the summer active period. Results. Results show that the fine structure of the kidney cortex is well preserved during hibernation. In the renal corpuscle, a sign of slight lesi on was the focal presence of oedematous endothelial cells and/or podocytes. Proximal convoluted tubule cells showed fully preserved ultrastructure and polarity, and hypertrophic apical endocytic apparatus. Structural changes were associated with increased plasma electrolytes, creatinine and urea nit rogen, and proteinuria. During the process of arousal the fine structure of the kidney cortex was also well. maintained. Conclusion. These results demonstrate that dormice are able to fully preser ve kidney cortex structure under extreme conditions resembling e.g. severe ischaemia or hypothermic organ storage for transplantation, and reperfusion . Elucidation of the mechanisms involved in such a natural model of organ p reservation could be relevant to human medicine.