Comparison of solutions for preservation of the rabbit liver as tested by isolated perfusion

The University of Wisconsin (UW) solution consists of a relatively complex mixture of agents. In this study we compared simpler preservation solutions, namely, histidine-tryptophan-ketoglutarate glutarate (HTK) and phosphatebuffered sucrose (PBS) with different compositions of UW solution in the isolated perfused rabbit liver model. Livers were stored cold for 24 and 48 h. After 24 h of preservation, the amount of bile produced in UW-preserved livers was significantly greater (P<0.05) than that in HTK-preserved livers. Also, there was less LDH released into the perfusate in UW-preserved livers. There was more edema and lower K+/Na+ rations in HTK-preserved livers than in UW-preserved livers (all data P<0.05). After 48 h of preservation, the differences between livers preserved in UW or HTK solution were less noticeable than at 24 h and bile production was similar. LDH and AST release were greater in HTK-preserved livers than in UW livers, but these differences were not statistically significant. Preservation in PBS for 48 h was worse than in either UW or HTK solution. Substitution of polyethylene glycol (PEG) for hydroxyethyl starch (HES) in 48-h UW-preserved livers was not effective. We conclude that solutions simpler in composition than UW solution may be effective in kidney transplantation but do not appear suitable for successuful liver preservation.     

An analysis of the components in UW solution using the isolated perfused rabbit liver

The isolated perfused rabbit liver model has been used to determine the essential components of the UW solution for hepatic preservation by simple cold storage. Livers were stored on ice for 48 hr after initial flushing with the solution being tested, and then reperfused at 38 degrees C in an isolated perfusion circuit; bile flow and enzyme (SGOT, SGPT, and LDH) release during a 2-hr period were recorded. All solutions tested contained phosphate (25 mM) as a buffer and magnesium sulfate (5 mM). Sodium can be substituted for potassium without adverse effects. Lactobionate, raffinose and glutathione cannot be omitted; all other components can be eliminated without altering the effectiveness of the solution in this model.     

Efficacy of polyethylene glycols in University of Wisconsin preservation solutions: a study of isolated perfused rat liver

Recent reports argue that the performance of University of Wisconsin (UW) solution is limited by the presence of hydroxyethyl starch (HES) as an additive, since HES could be responsible for human red blood cell aggregation. We investigated the effect on rat liver preservation of replacing HES in UW solution by polyethylene glycols (PEG20 and PEG35) at two concentrations. An isolated perfused rat liver model was used. Six groups of preserved livers (n = 7 for each group) were compared to controls (nonpreserved livers, n = 7). The following preservation solutions were assayed: UW without oncotic supply, UW-HES (0.25 mmol/L), UW-PEG20 (0.03 and 0.25 mmol/L), and UW-PEG35 (0.03 and 0.25 mmol/L). After 24-hour cold storage, the livers were perfused for 120 minutes at 37 degrees C with oxygenated Krebs-Henseleit solution. During perfusion, transaminase release, portal and bile flows, and bromosulfophthalein (BSP) clearance were assessed. Results showed that the omission of oncotic supply in UW statistically increased ALT and AST release in perfusate and decreased bile and portal flows. PEG addition in UW solution, especially PEG35 at 0.25 mmol/L, effectively protected the rat liver graft from the onset of hypothermic ischemia/reperfusion damage. In conclusion, data reported here reveal that oncotic supply is essential for liver preservation and that HES can be effectively replaced by PEG in UW solution.     

Relaxin as a protective substance in preservation solutions for organ transplantation, as shown in an isolated perfused rat liver model

Reperfusion injury, a well-known problem in organ transplantation, results from multiple pathologic mechanisms, including platelet/mast cell activation and peroxidation of cell membrane lipids. Relaxin was originally described as an insulin-like hormone produced in the ovaries during pregnancy. It causes vessel dilation and inhibition of platelet and mast cell activation. The present study investigated the protective effect of relaxin against reperfusion injury in liver tissue. We used a model of isolated perfused rat liver to simulate liver transplantation. Organ preservation was performed identical to human transplantation in 20 male Wistar rats. During preservation we applied 64 ng/mL relaxin. In contrast controls (n = 10) had no relaxin treatment. To quantify cell damage, we measured malonyldialdehyde (MDA; end product of lipid peroxidation) and myeloperoxidase activity (MPO; marker for accumulation of neutrophil granulocytes) in the perfusates. The livers were examined immunohistochemically for the same parameters. Relaxin as an additional substance in preservation solutions decreased perfusate MPO and MDA levels by up to 30%, as shown by immunohistochemistry. Our preliminary data suggested that relaxin is a promising agent to reduce hepatocyte damage caused by ischemia-reperfusion injury. Quantitative analysis of MDA and MPO levels in the perfusate is the subject of an ongoing study.     

Evaluation of a preservation solution containing fructose-1,6-diphosphate and mannitol using the isolated perfused rat kidney. Comparison with Euro-Collins and University of Wisconsin solutions

The renal preservation ability of a flushing solution (F-M)with fructose-1,6-diphosphate (1 g/dl) and mannitol (2 g/dl)during cold ischaemia was studied with the isolated perfusedrat kidney model and compared with the Euro-Collins (EC) andUniversity of Wisconsin (UW) solutions. Kidneys were storedin hypothermia for 4 and 18 h after initial flushing with thesolution being tested, and then reperfused at 37°C in anisolated perfusion circuit for 90 min with a Krebs-Henseleitsolution containing 4.5% albumin. Forty-four kidneys were studied and divided in a control groupand six study groups according to the cold ischaemia time andflushing solution used. Renal functional parameters of plasmaflow rate (PFR), renal vascular resistance (RVR), urine flowrate (UFR) glomerular filtration rate (GFR), fractional (FRNa)and net (TNa) sodium reabsortion were assessed during reperfusion.Conventional histology and malon-dialdehyde tissue levels (MDA)were also evaluated. Our results show that PFR, RVR, and UFR were similar in allstudy groups. After 4 and 18 h of cold ischaemia, GFR, FRNaand TNa were better, and conventional histology worse in F-Mthan in EC flushed kidneys. After 4 and 18 h of cold ischaemia,GFR, FRNa and TNa, in fact, were not different between F-M andUW flushed kidneys. After 4 h of cold ischaemia, conventionalhistology was similar in F-M and UW flushed kidneys. Nevertheless,after 18 h of cold ischaemia, UW flushed kidneys showed worsehistological parameters than F-M flushed kidneys. After 4 hof cold ischaemia, MDA was similar in kidneys flushed with thethree solutions. After 18 h of cold ischaemia MDA was higherin EC than in F-M or UW flushed kidneys. In summary, our newly developed cold storage solution showspromising results in renal preservation and its ability to preserveis at least as good as UW solution assessed in the isolatedperfused rat kidney.     

初始灌注液对离体低温保存大鼠肝脏的影响

目的 探讨缺血再灌注过程中初始灌注液对离体低温保存大鼠肝脏的影响。方法采用离体大鼠肝脏低温缺血保存再灌注模型90例,分别选择UW液、HC-A液和乳酸林格液作为不同的初始灌注液,观察大鼠肝脏在低温保存0、3、6、12、24 h后再灌注流出液中ALT、AST、LDH和ET的水平,同时比较3组之间肝脏细胞形态和细胞凋亡。结果 使用HC-A液作为初始灌注液的大鼠肝脏再灌注流出液中ALT、AST、LDH和ET水平较其他两组低(P<0.05),肝脏形态和细胞凋亡的发生3组差异无显著性。另外,上述指标均受低温保存时间的影响。结论 初始灌注液可影响离体低温保存大鼠肝脏的质量,细胞凋亡可能参与了肝脏的缺血再灌注损伤。     

Evaluation of eight preservation solutions for endothelial in situ preservation

BACKGROUND: Non-heart-beating donors (NHBDs) have the potential to reduce the increasing numbers of patients on kidney and liver graft waiting lists. One problem observed with kidneys obtained from NHBDs is the endothelial injury seen on protocol core biopsies after implantation. We postulate that this is caused by a combination of warm ischemia, cold ischemia, and hypertonic citrate during in situ preservation (ISP) rather than hypothermic machine preservation. Our aim was to optimize ISP methods to preserve endothelial structure and function. METHODS: An animal model of ISP was used to compare the ability of eight different preservation solutions to protect mammalian vascular tissue exposed to a combination of warm and cold ischemia. Smooth muscle contractile function and endothelial dependent relaxation (nitric oxide production) were determined using an organ bath method. RESULTS: Bretchneider's HTK solution preserved the ability of endothelial tissue to relax vascular tissue in response to acetylcholine (91% relaxation vs. 17% saline control; ANOVA, P<0.001); in stark contrast, Marshall's solution performed no better than saline (15% relaxation vs. 17% saline control, P=NS). UW solution (80%) and a derivative lacking the starch colloid (70%) were comparable with HTK. Belzer-MPS (55%), Celsior (57%), and Perfadex (44%) showed a roughly equivalent level of endothelial preservation. Electron microscopy confirmed an anatomical loss of structure correlating with loss of function. CONCLUSIONS: ISP requires a large volume of fluid to be pumped at high flow rates. In this model, HTK retained a powerful ability to preserve endothelial structure and function during warm ischemia.     

Glutathione in the isolated perfused rabbit kidney

Perfusion of the isolated rabbit kidney at normothermia leads to a marked depletion in the concentration of reduced glutathione in the kidney tissue. After 90 min of perfusion at 36 ± 1°C, the concentration of GSH found in the renal cortex is more than 80% lower than the levels found in fresh tissue. Comparable perfusion under hypothermic conditions reduced the amount of glutathione depletion considerably; however, after 90 min of perfusion at 15 ± 1°C, renal cortex GSH levels were still nearly 50% lower than the levels found in fresh tissue. It was found that the addition of GSH to the perfusate completely alleviated this glutathione-depletion phenomenon.     

Optimal hypothermic preservation of arrested myocardium in isolated perfused rabbit hearts: a 31P NMR study

The purpose of this study was to (1) relate myocardial high-energy phosphate stores to functional recovery after ischemia and reperfusion, (2) assess the bioenergetics and functional influence of clinically relevant myocardial hypothermia, and (3) examine tissue pH as an independent indicator of postischemic recovery of function. Rabbit hearts were perfused via a modified Langendorff technique, monitored for developed pressure (DP) and left ventricular end-diastolic pressure (LVEDP) via an isovolumic left ventricular balloon catheter, and placed in a Brucker NMR magnet (4.7 tesla) to measure phosphocreatine (PCr), adenosine triphosphate (ATP), and pH. Hearts underwent 1 hour of global ischemia at 7 degrees, 17 degrees, 27 degrees and 37 degrees C initiated by one dose of K+ cardioplegia followed by 30 minutes of reperfusion. After reperfusion, DP (expressed as a percentage of preischemic control) and LVEDP (mm Hg) in 7 degrees and 17 degrees C hearts were no different (96 + 5% vs 97 +/- 3%; 5 +/- 2 mm Hg vs 6 +/- 2 mm Hg; p = NS), but were better (p less than 0.01) than 27 degree hearts (72 +/- 6%, 17 +/- 6 mm Hg) and 37 degree hearts (31 +/- 7%, 60 +/- 6 mm Hg). PCr was severely depleted in all groups. ATP was 90 +/- 7% and 87 +/- 5% of preischemic control in the 7 degree and 17 degree hearts, which was significantly better than the 68 +/- 3% and 21 +/- 3% in the 27 degree and 37 degree groups (p less than 0.01). The pH at end ischemia was 6.83, 6.89, 6.54, and 5.86 for the 7 degree, 17 degree, 27 degree, and 37 degree hearts, respectively (7 degrees vs 27 degrees or 37 degrees, p less than 0.01; 17 degrees vs 27 degrees or 37 degrees, p less than 0.01). Linear regression of DP on end-ischemic ATP (EIATP) and end-ischemic pH revealed: DP = 0.96 (EIATP) + 20 (r = 0.92) and DP = 60 (pH) -317 (r = 0.86). We conclude that (1) end-ischemic ATP predicts recovery of ventricular function, and, furthermore, there appears a threshold ATP concentration (80% of control) below which full recovery of function will not occur; (2) end-ischemic pH predicts recovery of ventricular function; (3) 7 degrees C hypothermic ischemia does not cause a clinically significant cold injury; and (4) in a single-dose crystalloid cardioplegia model, end-ischemic pH is linearly related to recovery of function (r = 0.86).     

Evaluation of citrate flushing solution using the isolated perfused rat kidney

The isolated rat kidney perfused at 37 C with dialyzed bovine serum albumin (6.5 g/100 ml) in Krebs-Henseleit buffer was used to examine why a hypertonic citrate flush permits rapid recovery of renal function after storage. The composition of the original hyperosmolar citrate solution was varied so that the roles of osmolality, magnesium, and citrate could be evaluated. All kidneys were flushed with the test solutions and stored for 24 hr in the test solutions at 0 C. The citrate flushing solution requires both the citrate anion and magnesium for efficacy. Hyperosmolality does not enhance its action, an isosmolar solution is more effective. Citrate can be replaced by a nonmetabolizable analogue, tricarballylate, if the solution is suitably buffered. The mechanism of action of citrate is still uncertain, it does not seem primarily to act as a metabolic fuel or inhibitor.     

Effects of taurine on liver preservation in UW solution with consecutive ischemic rewarming in the isolated perfused rat liver

Taurine (2-aminoethane sulfonic acid) is a physiologic amino acid involved in cellular osmoregulation in various species including man. This study was intended to compare the respective effects of cold storage and consecutive ischemic rewarming of the liver on postischemic hepatic flow and hepatocellular outcome upon reperfusion with or without the addition of taurine to the preservation medium. Livers from male Wistar rats were rinsed free of blood via the portal vein and stored ischemically at 4 °C in UW solution. Livers from group 1 were then rinsed again with 10 ml Ringer's solution and reperfused with Krebs-Henseleit buffer at a constant pressure of 10 mmHg for 45 min at 37 °C in a nonrecirculating manner. Livers from groups 2 and 3 were subjected to 30 min of warm ischemia subsequent to cold storage and prior to reperfusion with 10 mM taurine added to the UW solution in group 3. While there were only very few signs of hepatic injury in group 1, the additional period of warm ischemia (group 2) led to a significant reduction in early perfusate flow and enhanced enzyme leakage from the livers during postischemic rinse and reperfusion. Livers in group 3 exhibited an amelioration in hepatic circulation and significantly reduced enzyme release as compared to group 2. The results clearly demonstrate a remarkable impact of postischemic rewarming on graft viability. Furthermore, the addition of taurine to the preservation medium was shown to improve hepatic circulation and enhance viability of the liver upon reperfusion.     

Amrinone preconditioning in the isolated perfused rabbit heart

BACKGROUND: Ischemic preconditioning (IPC) reduces infarct size in experimental preparations. IPC, however, is not without detrimental effects. We studied amrinone as a possible alternative to IPC. METHODS: Isolated perfused rabbit hearts were given a 5-minute infusion of 10 micromol/L amrinone followed by a 5-minute washout (n = 6). The anterior descending artery was then occluded for 1 hour and reperfused for 1 hour. Six hearts underwent IPC, with two episodes of 5-minute global ischemia followed by 5-minute reperfusion before LAD occlusion; eight control hearts received no preconditioning. Left ventricular pressure and ischemic zone epicardial monophasic action potentials were continuously monitored. RESULTS: IPC but not amrinone reduced peak pressure before anterior descending artery occlusion. Peak pressure fell significantly during ischemia and reperfusion in all hearts. End diastolic pressure rose significantly during reperfusion in control and IPC hearts but not in amrinone hearts. Action potentials shortened during ischemia in all hearts. They returned to preocclusion values in control hearts but lasted beyond preocclusion values in IPC and amrinone hearts. Both the incidences of ventricular fibrillation and infarct size were significantly reduced in amrinone hearts but not in IPC hearts. CONCLUSIONS: Amrinone is not only a useful inotropic agent but is also a superior preconditioning agent when compared to IPC.     

Extraction of glutathione by the isolated perfused rabbit kidney

The effects of adding exogenous reduced glutathione (GSH) to the perfusate were studied in the isolated perfused rabbit kidney. The addition of 500 mg/liter of GSH to the perfusate prevented the depletion of cortical and medullary GSH; perfusion without the addition of GSH consistently resulted in depletion of tissue levels of this tripeptide. In addition, GSH supplementation of the perfusate decreased renal vascular resistance and increased perfusate flow. GSH extraction studies revealed a progressive decrease in renal extraction with time, ranging from complete extraction at 10 min to a value of 38% at 60 min. The fractional clearance of GSH increased from 7.3% at 10 min to 17.9% after 60 min of perfusion. The results indicate a high affinity of the rabbit kidney for GSH and a relatively large net reabsorption of the tripeptide.