Allopurinol improves scavenging ability of the liver after ischemia/reperfusion injury.

Deterioration of energy metabolism and oxidative stress represent fundamental mechanisms in ischemia and reperfusion injury. In a normothermic ischemia/reperfusion rat model, we investigated whether allopurinol (ALL) may improve the scavenging ability of the liver after ischemia. ALL was given prior to ischemia and reperfusion (concentration 100 or 50 mg/kg) and controls were given a placebo. After a basal period of 30 min, 1 h normothermic ischemia was induced in the median and left liver lobes followed by 24 h observation. The overall liver function was assessed by bile secretion, and free oxygen production was assessed by glutathione efflux into bile during the first 60 min of reperfusion and at 24 h. Allopurinol (concentration 100 mg/kg) protected hepatocyte function as bile flow improved significantly in this group after 1 and 24 h of reperfusion compared with that of controls. Oxidative stress was also significantly attenuated in this group, as efflux of glutathione into bile was significantly higher in the ALL group (100 mg/kg) after 24 h but not after 1 h of reperfusion compared with that of controls. All given in a concentration 50 mg/kg had some, but a non-significant, effect. We conclude that biliary glutathione is an important marker of oxidative stress and may reflect the scavenging ability of the liver after ischemic injury. Significant correlation of bile flow with biliary glutathione during reperfusion indicates that oxidative stress is an important mechanism attenuating liver function after ischemia/reperfusion injury.

Protective effects of the calcium channel blocker verapamil on hepatic function following warm ischemia.

The purpose of this study was to investigate the protective effects of the calcium channel blocker verapamil on warm ischemia-reperfusion injury to the liver using a rat model. Ischemia of the left and median lobes was created by total inflow occlusion for 60 min followed by 24 hr of reperfusion. Hepatocell injury was assessed by the release of liver enzymes [alanine aminotransferase (ALT) and lactic dehydrogenase (LDH)], reduced (GSH) and oxygenated (GSSG) plasma glutathione and total biliary glutathione. Hepatocyte function was quantitated by measuring bile flow. Rats were randomized to one of two groups: pretreatment with iv verapamil (0.3 mg/kg) or iv normal saline (controls). Verapamil significantly increased bile flow and GSH efflux while decreasing plasma ALT and LDH compared to those in controls 24 hr after liver ischemia-reperfusion (LIR). A significant correlation existed between bile flow and biliary GSH efflux at 1 but not 24 hr after LIR, suggesting that early LIR injury is mediated predominantly by generation of oxygen free radicals. Liver enzyme elevation and bile flow were inversely correlated at 24 but not 1 hr after injury. We conclude that verapamil significantly protects the liver against warm LIR injury. The minimal protective effect of verapamil on early liver ischemia-reperfusion demonstrates that verapamil does not prevent the early generation of oxygen radicals upon reperfusion. However, the significant restoration of biliary GSH efflux and hepatocyte protection at 24 hr suggests involvement of calcium ions in late hepatocyte injury. Verapamil's protective effects may be related to attenuating pathophysiologic events occurring beyond 1 hr of reperfusion. Future studies investigating the protective effects of verapamil on warm LIR injury should be carried out for at least 24 hr postreperfusion.

Allopurinol dose is important for attenuation of liver dysfunction after normothermic ischemia: correlation between bile flow and liver enzymes in circulation.

We have investigated the effect of two doses of allopurinol (ALL) (100 and 50 mg/kg) administered i.v. on liver function after 1 h of normothermic ischemia. ALL given in a concentration of 100 mg/kg significantly improved bile output after 1 and 24 h of reperfusion. Hepatocyte injury reflected by alanine aminotransferase (ALT) and lactic dehydrogenase (LDH) in plasma was also significantly reduced at 24 h, but not at 1 h of reperfusion compared with controls. ALL administered at a concentration of 50 mg/kg had some protective effect. Significant correlation between circulating liver enzymes and bile output at 24 h after reperfusion indicates an important pathophysiologic link between hepatocyte function and injury in this time window.

Effect of allopurinol on the concentration of endogenous glutathione in hepatocytes after an hour of normothermic liver ischemia.

OBJECTIVE: To find out whether oxygen free radical liberated by activation of xanthine oxidase change the tissue concentration of glutathione. DESIGN: Controlled study. MATERIAL: 42 male Wistar rats. INTERVENTION: Laparotomy, induction of ischemia, and reperfusion. 27 rats were treated with allopurinol (to inhibit xanthine oxidase) and the remaining 15 acted as controls. MAIN OUTCOME MEASURES: Concentrations of reduced glutathione, oxidized glutathione, and total glutathione in hepatocytes, blood, and bile. RESULTS: Concentration of reduced and total glutathione in hepatocytes decreased significantly during reperfusion and oxidized glutathione was unchanged in all groups. Total glutathione in peripheral venous blood was reduced by half during the period of ischemia and increased gradually during reperfusion whereas the concentration of total glutathione in bile decreased appreciable during reperfusion. Production of bile improved significantly during reperfusion in the group treated with allopurinol compared with the control group. CONCLUSION: Xanthine oxidase may not be the main source of production of oxygen free radicals as allopurinol did not affect the hepatic concentration of glutathione during reperfusion.

Normothermic liver ischemia in rats: xanthine oxidase is not the main source of oxygen free radicals.

We studied the effect of allopurinol (ALL) on the activity of xanthine dehydrogenase (XDH), xanthine oxidase (XOX), superoxide dismutase (SOD), and catalase (CAT) in rat liver during ischemia followed by 60 min of reperfusion. We induced 60-min ischemia in the median and left lobes by clamping the hepatic artery and portal branches. The percentage XOX relative to total oxidase activity increased significantly in the control group, from 10% during the stabilization period to 18% after 60 min of reperfusion. The XDH activity decreased during reperfusion. Activity of both XDH and XOX was almost completely blocked by ALL. The activity of SOD and CAT did not differ significantly between the ALL group and controls after 60 min of reperfusion. ALL treatment did not affect liver injury parameters, as concentrations of lactate dehydrogenase (LDH) and alanine transferase (ALT) increased in plasma after ischemia, both in controls and in the ALL-treated group. We concluded that ischemia promotes conversion of XDH to XOX during reperfusion. XOX may not be the main source of free radical production, since intracellular scavengers (SOD and CAT) did not differ significantly between controls and the ALL-treated group, despite the fact that ALL blocked XOX activity completely.

Sixty minutes normothermic ischemia in rat liver: the declining tissue concentration of hypoxanthine during reperfusion is not a washout phenomenon.

A rat liver normothermic ischemia-reperfusion model was used to investigate whether hypoxanthine (HXA) that accumulated during ischemia was washed out in hepatic veins during reperfusion. Ischemia was induced in median and left lobes by clamping of the proper hepatic artery and portal branches. The effect of allopurinol (ALL) on metabolism of ATP and HXA was studied before, during and after a 60-min normothermic ischemic insult. Liver cell concentration of HXA in the group treated with ALL increased during ischemia and decreased rapidly during the first 10-min reperfusion. Recovery of ATP increased gradually during the 10-min reperfusion period and was significantly higher in the group treated by ALL compared to that of controls. Liver venous blood concentration of HXA in the ALL-treated group was 10-to 40-fold lower than that in liver tissue. The rapidly decreasing concentration of HXA in liver tissue during reperfusion and a minimal washout may indicate that HXA was used for resynthesis of ATP during reperfusion.

Sixty-minute normothermic liver ischemia in rats. Evidence that allopurinol improves liver cell energy metabolism during reperfusion but that timing of drug administration is important.

Allopurinol (ALL) improves energy metabolism in organs subjected to ischemia-reperfusion injury. The importance of different administration schedules of ALL has been studied in a rat liver model exposed to 60 min of normothermic ischemia followed by reperfusion. ALL (100 mg/kg) that administered in two doses, one prior to ischemia and one prior to reperfusion, improved production of adenosine triphosphate in the liver as well as bile flow during reperfusion. ALL administered in a single dose, either prior to ischemia or prior to reperfusion, was less effective. The concentration of hypoxanthine during ischemia increased in the groups given ALL prior to induction of ischemia. Based on the present findings, we argue that the beneficial effect of ALL administration can be potentiated by different drug-administration schedules. Our data also suggest that the prime mechanism of action for ALL is not only related to inhibition of free-oxygen-radicals production but that preservation of hypoxanthine, which can be used for ATP resynthesis and the scavenging properties of ALL itself, may be equally important.

60 min normothermic liver ischemia in rats: allopurinol improves energy status and bile flow during reperfusion.

The effect of allopurinol was studied in a normothermic liver ischemia rat model. Functional (bile flow) and biochemical parameters (high-energy phosphates, ATP, ADP, AMP), energy charge, hypoxanthine and xanthine were determined prior to and during 60 min of ischemia followed by 120 min of reperfusion. Allopurinol given in the preischemic period (50%) and as a bolus (50%) prior to reperfusion improved liver function significantly, whereas allopurinol given in the preischemic period (50%) and after start of reperfusion (50%) had no effect. The data indicates that allopurinol given prior to reperfusion saved hypoxanthine which was used for ATP resynthesis during reperfusion.

Sixty minutes of normothermic ischemia in the rat liver: correlation between adenine nucleotides and bile excretion.

The effect of 60 min of normothermic liver ischemia on cellular levels of adenine nucleotides (ATP, ADP, and AMP), energy charge (EC), and bile excretion was studied. Following ischemia the concentration of ATP was reduced to 12% of preischemic and control values within the first 10 min and remained low during the remaining ischemic period. EC values were also low. During 120 min of reperfusion, ATP increased to 34% of the ATP level found in the control group. EC values increased immediately to reach values not significantly different from those of control animals. Bile flow was nonexistent during ischemia and increased during reperfusion. The increase paralleled those of ATP and EC. Bile flow seems to reflect the degree of liver ischemia and may be used as a functional parameter.

Sudden death caused by heart block in a patient with multiple myeloma and cardiac amyloidosis.

A patient with multiple myeloma and amyloidosis was admitted to hospital following successful cardiopulmonary resuscitation at home. No disturbances in heart rhythm were seen during the first 48 hours of continuous telemetric ECG recording. The patient died from ventricular asystole due to complete atrioventricular block, while he was on a 24-hour Holter monitoring the fifth night in hospital. Patients with known cardiac amyloidosis and syncope should undergo long-term ECG recordings, preferably by telemetry. Repeated registrations may be necessary to discover disturbances in heart rhythm.