Role of peroxynitrite anion in renal hypothermic preservation injury.

BACKGROUND: Peroxynitrite anions may play a role in normothermic renal ischemia and reperfusion. The purpose of this study was to determine if endogenous peroxynitrite anion is involved in renal preservation injury. METHODS: Experiments were conducted in isolated canine renal tubules and in a canine autotransplant model of hypothermic preservation injury. RESULTS: Isolated renal tubules demonstrated progressive loss of membrane transport function after reperfusion with increasing cold storage times in UW solution as assessed by tetraethylammonium cation transport (TEA). This transport defect was not altered by reperfusion in the presence of WW85, a peroxynitrite decomposition catalyst. Likewise, tubule LDH release was not altered by WW85. Renal tubules did not demonstrate any evidence of peroxynitrite formation after cold storage (0-120 h) or after subsequent reperfusion in vitro as measured by nitrotyrosine adduct formation. Addition of exogenous peroxynitrite (1 mM) directly to freshly isolated renal tubules produced strong nitrotyrosine signals but failed to alter membrane function (TEA uptake). Conversely, SIN-1, a peroxynitrite generator molecule, failed to produce a nitrotyrosine signal in extracted renal tubule proteins but significantly impaired transport function. Finally, function of cold stored canine autografts was not affected by the scavenging of peroxynitrite anions (WW85) before kidney harvest and immediately at reperfusion. Tissue biopsies from cold stored kidney autografts also failed to show evidence of peroxynitrite synthesis either after cold storage (72 h) or after kidney transplantation (60 min reperfusion). CONCLUSIONS: This study concludes that peroxynitrite anions are not formed and are not involved in renal preservation injury.

Ischemic preconditioning and liver tolerance to warm or cold ischemia: experimental studies in large animals.

BACKGROUND: In the rodent, ischemic preconditioning (IPC) has been shown to improve the tolerance of the liver to ischemia-reperfusion under normothermic or hypothermic conditions. The aim of the present study was to test this hypothesis in a dog model, which may be more relevant to the human. METHODS: Beagle dogs were used in two distinct animal models of hepatic warm ischemia and orthotopic liver transplantation (hypothermic ischemia). IPC consisted of 10 minutes of ischemia followed by 10 minutes of reperfusion. In the first model, livers were exposed to 55 minutes prolonged warm ischemia and reperfused for 3 days (n = 6). In the second model, livers were retrieved and preserved for 48 hours at 4 degrees C in University of Wisconsin solution, transplanted, and reperfused without immunosuppression for 7 days (n = 5). In each model, nonpreconditioned animals served as controls (n = 5 in each group). Also, isolated dog hepatocytes were subjected to warm and cold storage ischemia-reperfusion to model the animal transplant studies using IPC. RESULTS: In the first model (warm ischemia), IPC significantly decreased serum aminotransferase activity at 6 and 24 hours post-reperfusion. After 1 hour of reperfusion, preconditioned livers contained more adenosine triphosphate and produced more bile and less myeloperoxidase activity (neutrophils) relative to controls. In the second model (hypothermic preservation), IPC was not protective. Finally, IPC significantly attenuated hepatocyte cell death after cold storage and warm reperfusion in vitro. CONCLUSIONS: IPC is effective in large animals for protecting the liver against warm ischemia-reperfusion injury but not injury associated with cold ischemia and reperfusion (preservation injury). However, the IPC effect observed in isolated hepatocytes suggests that preconditioning for preservation is theoretically possible.

Brain death does not affect hepatic allograft function and survival after orthotopic transplantation in a canine model.

BACKGROUND: Brain death has been shown to decrease graft function and survival in rodent models. The aim of this study was to evaluate how brain death affects graft viability in the donor and liver tolerance to cold preservation as assessed by survival in a canine transplant model. METHODS: Beagle dogs were used for the study. Non-brain dead (BD) donors served as controls. Brain death was induced by sudden inflation of a subdural balloon catheter with continuous monitoring of arterial blood pressure and electroencephalographic activity. Sixteen hours after confirmation of brain death, liver grafts were retrieved. All livers were flushed in situ and preserved for 24 hr in cold University of Wisconsin solution before transplantation. Recipient survival rates, serum hepatic enzyme levels, coagulation, and metabolic parameters of the recipients were analyzed. RESULTS: No significant changes were observed in serum aminotransferases (alanine and aspartate transaminases) and lactate dehydrogenase levels in the BD donor. After preservation, control (n=6) and BD livers (n=5) showed full functional recovery after transplant with 100% survival in both groups at day 7. There was no significant difference in peak serum alanine, aspartate transaminases, and lactate dehydrogenase after transplantation in recipients who received a liver from BD donor compared to control group. BD livers were functionally as capable as control livers in correcting metabolic acidosis during the first 24 hr posttransplantation. Coagulation profiles (index normalized ratio, activated partial thromboplastin time) after reperfusion were similar between groups. CONCLUSION: In contrast to previous reports in rodent models, our study shows that brain death does not cause significant liver dysfunction in the donor before organ removal. Donor brain death and prolonged liver graft preservation do not interact significantly to impair liver function and survival after transplantation.