Xanthine oxidase mediates myocardial injury after hepatoenteric ischemia-reperfusion

OBJECTIVES: To determine if myocardial injury results from hepatoenteric ischemia-reperfusion. We also proposed to determine if this remote heart injury is mediated by a xanthine oxidase-dependent mechanism. DESIGN: Randomized, controlled animal study. SETTING: University-based animal research facility. SUBJECTS: Thirty-six New Zealand white male rabbits, weighing 1.8 to 3 kg. INTERVENTIONS: Anesthetized rabbits were randomly assigned to one of four groups (n = 9 per group): a) a sham-operated group; b) a sham-operated group pretreated with sodium tungstate (xanthine oxidase inactivator); c) an aorta occlusion group; and d) an aorta occlusion group pretreated with sodium tungstate. Descending thoracic aorta occlusion was maintained for 40 mins with a 4-Fr Fogarty embolectomy catheter, followed by 2 hrs of reperfusion. MEASUREMENTS AND MAIN RESULTS: Myocardial injury, manifested by increased circulating creatine kinase-MB fraction activity, was significantly associated with aortic occlusion and reperfusion (p < .05). Sodium tungstate pretreatment significantly (p < .05) reduced circulating and myocardial xanthine oxidase activity. Xanthine oxidase inactivation by sodium tungstate significantly decreased circulating creatine kinase-MB fraction activity after hepatoenteric ischemia-reperfusion (p < .05). Finally, circulating creatine kinase-MB fraction activity was significantly associated with circulating xanthine oxidase activity (r2 = .85; p < .001). CONCLUSIONS: We conclude that remote myocardial injury is caused by hepatoenteric ischemia-reperfusion. The pathoetiology of this myocardial injury involves a xanthine oxidase-dependent mechanism.     

Direct induction of acute lung and myocardial dysfunction by liver ischemia and reperfusion

OBJECTIVES: To investigate whether liver ischemia and reperfusion (IR) directly affect functions of remote organs. BACKGROUND: Cardiovascular and respiratory dysfunction follows hemorrhage, spinal shock, or trauma as a result of no-flow-reflow phenomena. Hepatic IR induces remote organ damage probably by xanthine oxidase and oxygen species. MATERIALS AND METHODS: Isolated rat livers, lungs, and hearts were perfused with Krebs-Henseleit solutions. After stabilization, livers were either perfused or made ischemic. Then, livers and hearts or livers and lungs were reperfused in series, and the liver was disconnected and the second organ continued to perfuse with the accumulated effluents. MEASUREMENTS AND MAIN RESULTS: Ischemic and reperfused liver effluent contained high lactate dehydrogenase and uric acid concentrations compared with controls; xanthine oxidase increased 60 to 100 times. Ischemic and reperfused lung peak inspiratory pressure almost doubled; airway static compliance halved; myocardial contractility decreased to 70% of baseline; wet weight-to-dry weight ratios of lungs and livers increased. CONCLUSION: Ischemic and reperfused liver can directly induce myocardial and pulmonary dysfunction, presumably by oxidant-induced injury.     

Immunogenicity, safety and efficacy of tetravalent rhesus-human, reassortant rotavirus vaccine in Belém, Brazil

The ESR signal of NO bound to hemoglobin was detected during the ischemia-reperfusion of myocardium with low temperature ESR technique, and the synergic effects of NO and oxygen free radicals in the injury of the process were studied with this technique. Oxygen free radicals and NO bound to beta-subunit of hemoglobin (beta-NO complex) could be detected simultaneously in the ischemia-reperfused myocardium. Those signals could not be detected from the normal myocardium even in the presence of L-arginine. However, those signals could be detected and were dose-dependent with L-arginine in the ischemia-reperfused myocardiums and the signal could be suppressed with the inhibitor of NO synthetase, NG-nitro-L-arginine methylester (NAME). Measurement of the activities of lactate dehydrogenase (LDH) and creatine kinase (CK) in the coronary artery effluent of ischemia-reperfused heart showed that L-arginine at lower concentration (< 1 mmol/L) could protect the heart form the ischemia-reperfusion injury but at higher concentration aggravate the injury. Addition of NAME to the reperfusion solution could also protect the myocardium. Addition of xanthine (X)/xanthine oxidase (XO) or Fe2+/H2O2 to the reperfusion solution increased the production of NO and oxygen free radicals and the ischemia-reperfused injury simultaneously. Addition of superoxide dismutase (SOD) and catalase decreased the production of NO and oxygen free radicals and the ischemia-reperfusion injury.     

Enhanced ketogenesis in the kidney during hepatic inflow occlusion with the administration of Ringer's acetate solution

BACKGROUND: The blood levels of ketone bodies, which are synthesized principally in the liver, were maintained even during hepatic inflow occlusion if Ringer's acetate solution (AR) was administered, resulting in an improvement of hepatic energy level in the reperfusion phase, as reported in our previous experimental study. The current study was designed to prove that the kidneys are the organs that contribute to synthesize ketone bodies during hepatic inflow occlusion if AR is administered. METHODS: The arterial, central venous, renal venous, and renal tissue ketone body concentrations were determined in rabbits administered AR or Ringer's lactate solution (LR) at 20 minutes of hepatic ischemia and at 30 minutes of reperfusion. The concentrations were also compared in rabbits under AR infusion with or without hepatic ischemia for 20 minutes. Statistical analyses were performed by means of ANOVA: RESULTS: With AR the renal venous ketone body concentration not only was higher than that with LR (p < 0.001) but also was higher than the arterial concentration (p = 0.05). The renal tissue ketone body concentration was higher than in those with LR (p < 0.001) and also than in those without occlusion (p < 0.001). CONCLUSIONS: Ketogenesis is enhanced in the kidney and may compensate for hepatic loss of ketogenic function during hepatic inflow occlusion under AR administration.     

Is reperfusion injury an important cause of mucosal damage after porcine intestinal ischemia?

BACKGROUND: Intestinal ischemic injury is exacerbated by reperfusion in rodent and feline models because of xanthine oxidase-initiated reactive oxygen metabolite formation and neutrophil infiltration. Studies were conducted to determine the relevance of reperfusion injury in the juvenile pig, whose low levels of xanthine oxidase are similar to those of the human being. METHODS: Ischemia was induced by means of complete mesenteric arterial occlusion, volvulus, or hemorrhagic shock. Injury was assessed by means of histologic examination and measurement of lipid peroxidation. In addition, myeloperoxidase, as a marker of neutrophil infiltration, and xanthine oxidase-xanthine dehydrogenase were measured. RESULTS: Significant ischemic injury was evident after 0.5 to 3 hours of complete mesenteric occlusion or 2 hours of shock or volvulus. In none of these models was the ischemic injury worsened by reperfusion. To maximize superoxide production, pigs were ventilated on 100% O2, but only limited reperfusion injury (1.2-fold increase in histologic grade) was noted. Xanthine oxidase-xanthine dehydrogenase levels were negligible (0.4 +/- 0.4 mU/gm). CONCLUSIONS: Reperfusion injury may not play an important role in intestinal injury under conditions of complete mesenteric ischemia and low-flow states in the pig. This may result from low xanthine oxidase-xanthine dehydrogenase levels, which are similar to those found in the human being.     

Hypoxia-reoxygenation is as damaging as ischemia-reperfusion in the rat liver

OBJECTIVE: We hypothesized that the extent of injury and release of xanthine oxidase, an oxidant generator, into the circulation would be less in normal-flow hypoxia-reoxygenation than in equal duration no-flow ischemia-reperfusion. DESIGN: Randomized study. SETTING: University-based animal research facility. SUBJECTS: Male Sprague-Dawley rats. INTERVENTIONS: The livers were isolated, perfused, and then randomly subjected to 2 hrs of hypoxia (normal flow, low oxygen) or ischemia (no flow, no oxygen), and 2 hrs of reperfusion. Hepatocytes were also isolated, and were subjected to either: a) hypoxia (0, 2, 4, and 6 hrs); or b) hypoxia (2 and 4 hrs) with reoxygenation (2 hrs). MEASUREMENTS AND MAIN RESULTS: The extent of liver injury (as assessed by release of hepatocellular enzymes) and the release of xanthine oxidase were measured from isolated-perfused rat livers and cultured hepatocytes. The pattern of release of xanthine oxidase in isolated-perfused liver effluent was different in hypoxia-reoxygenation compared with ischemia-reperfusion. During hypoxia, xanthine oxidase gradually increased in the effluent; then, the xanthine oxidase decreased to low concentrations during reoxygenation. After ischemia, there was a sharp spike in xanthine oxidase at 1 min of reperfusion, with a rapid decrease to low concentrations. The total release of xanthine oxidase during hypoxia-reoxygenation was similar to that during ischemia-reperfusion. Lactate dehydrogenase and other markers of liver injury showed a pattern of release that was similar to that of xanthine oxidase, but the total release of markers was not different between the two groups. In hepatocytes, most of the release of enzymes occurred in hypoxia, and the rate of release was not different between hypoxia and hypoxia-reoxygenation. CONCLUSIONS: Hypoxia-reoxygenation results in as much damage to the liver as ischemia-reperfusion, and results in the release of a similar amount of oxidant-producing xanthine oxidase into the circulation.     

Reperfusion injury as the mechanism of brain damage after perinatal asphyxia

Upon reperfusion of ischemic tissues, reactive oxygen metabolites are generated and are responsible for much of the organ damage. Experimental studies have revealed two main sources of these metabolites: 1) the oxidation of hypoxanthine to xanthine and on to uric acid by the oxidase form of xanthine oxidoreductase and 2) neutrophils accumulating in ischemic and reperfused tissue. Blocking either source will reduce reperfusion damage in a number of experimental situations. Although xanthine oxidoreductase activity may be unmeasurably low in organs other than liver and intestine, it may be involved in reperfusion injury elsewhere because of its localization in capillary endothelial cells. Time course considerations suggest that substrate accumulation and NADH inhibition of dehydrogenase activity may be more important in the pathogenesis than conversion of xanthine dehydrogenase into the oxidase form. Neutrophil accumulation may be partly due to oxidants in the first place, suggesting a link between the two sources of reactive oxygen metabolites. In the clinical context, many of the sequelae of perinatal asphyxia may be accounted for by reperfusion damage to organs such as brain, kidney, heart, liver, and lungs. During asphyxia, substrates of xanthine oxidase accumulate, upon resuscitation the cosubstrate oxygen is introduced, and evidence for oxidant production and effects has been obtained. In the pathogenesis of brain damage after asphyxia, both microvascular injury and parenchymal cell damage are important. Oxygen metabolites are involved in the former, but in the latter process their role is less clear because ischemia-reperfusion triggers not only oxidant production but many other phenomena, including gene activation, ATP depletion, glutamate accumulation, and increase of intracellular calcium. A severe insult results in cell necrosis, but more moderate asphyxia may cause delayed neuronal death through apoptosis. The time course of the changes in high energy phosphates as well as of selective neuronal death suggest that in the first hours of life there is a "therapeutic window," with future possibilities for prevention of permanent damage.     

The effects of wound lavage solutions on canine fibroblasts: an in vitro study

OBJECTIVE: The purpose of this study was to determine the effects of phosphate-buffered saline (PBS), sterile tap water, normal saline, and Ringer's lactate on wound healing in an in vitro model. STUDY DESIGN: The effects of PBS, sterile tap water, normal saline, and Ringer's lactate on a primary line of canine embryonic fibroblasts were determined. ANIMALS OR SAMPLE POPULATION: A primary line of canine embryonic fibroblasts. METHODS: The effects of the various lavage solutions were determined by (1) vital staining of the treated cells with a 0.5% trypan blue solution, (2) evaluation of the amount of lactate dehydrogenase released by the treated cells, and (3) cytopathologic evaluation of hematoxylin and eosin-stained monolayers of treated canine fibroblasts. The cells were exposed to the lavage treatments for the following time intervals: 0.5 minute, 1 minute, 2.5 minutes, 5 minutes, and 10 minutes. PBS was used as the control. RESULTS: Sterile tap water significantly damaged canine fibroblasts at all time intervals (P = .05). This was attributed to the alkaline pH, hypotonicity, and presence of numerous cytotoxic trace elements in the tap water used. Cytotoxic effects were noted in fibroblasts after 10 minutes' exposure to normal saline; this may be because of the acidic pH of normal saline and lack of a buffering system. Ringer's lactate did not induce any significant fibroblast injury. CONCLUSIONS: PBS and Ringer's lactate do not induce any significant fibroblast injury, whereas normal saline and sterile tap water cause mild and severe cytotoxic effects in vitro. CLINICAL RELEVANCE: Further clinical investigation is indicated to establish whether Ringer's lactate is the wound lavage solution of choice compared with normal saline. Sterile tap water may cause considerable fibroblast injury.     

Desflurane increases pulmonary alveolar-capillary membrane permeability after aortic occlusion-reperfusion in rabbits: evidence of oxidant-mediated lung injury

BACKGROUND: Pulmonary injury occurs after vascular surgery, with xanthine oxidase (an oxidant generator) released from reperfusing liver and intestines mediating a significant component of this injury. Because halogenated anesthetics have been observed to enhance oxidant-mediated injury in vitro, the authors hypothesized that desflurane would increase alveolar-capillary membrane permeability mediated by circulating xanthine oxidase after thoracic occlusion and reperfusion. METHODS: Rabbits were assigned to one of five groups: aorta occlusion groups administered desflurane (n=14), desflurane and tungstate (xanthine oxidase inactivator, n=12), fentanyl plus droperidol (n=13), and two sham-operated groups (desflurane, n=7 and fentanyl plus droperidol, n=7). Aortic occlusion was maintained for 45 min with a balloon catheter, followed by 3 h of reperfusion. Alveolar-capillary membrane permeability was assessed by measurement of bronchoalveolar lavage fluid protein. Xanthine oxidase activity was determined in plasma and lung tissue. Ascorbic acid content (an antioxidant) was determined in lung tissue. RESULTS: Desflurane was associated with significantly increased alveolar-capillary membrane permeability after aortic occlusion-reperfusion when compared with the fentanyl plus droperidol anesthesia or sham-operated groups (P < 0.05). Inactivation of xanthine oxidase abrogated the alveolar-capillary membrane compromise associated with desflurane. Although significantly greater than for sham-operated animals, plasma xanthine oxidase activities released after aortic occlusion-reperfusion were not different between the two anesthetics. There were no anesthetic-associated differences in lung tissue xanthine oxidase activity. However, desflurane anesthesia resulted in a significant reduction in lung ascorbic acid after aortic occlusion-reperfusion compared with the sham-operated animals. CONCLUSIONS: Desflurane anesthesia increased xanthine oxidase-dependent alveolar-capillary membrane compromise after aortic occlusion-reperfusion in concert with depletion of a key tissue antioxidant.     

Generation of free radicals during anoxia and reoxygenation in perfused osteoblastlike cells

Sensitivity to ischemia and reperfusion injury is a main problem afflicting tissues exposed to a prolonged period of oxygen deprivation. The generation of oxygen free radicals, in particular, is considered a major cause of postischemic reperfusion injury. However, studies on the mechanisms of production of free radicals are limited by the difficulty to measure in real time their formation and to discriminate between the different oxyradical species. The aim of this study was to determine whether the formation of oxygen free radicals occurs in murine osteoblastlike cells (MC3T3-E1) exposed to anoxia and reoxygenation and to explore its relation to the reoxygenation injury. Cells were cast in agarose and perfused with oxygenated Krebs-Henseleit bicarbonate buffer. Anoxia was obtained by shifting the gas phase of the media to 95% N2-5% CO2. Oxygen free radicals were detected by enhanced chemiluminescence: anion superoxide or hydrogen peroxide was measured by adding lucigenin or luminol plus horseradish peroxidase to the media, respectively. Cell injury was assessed by the rate of lactate dehydrogenase release. During the control period, lucigenin and luminol plus horseradish chemiluminescences were 15 +/- 1 nA per chamber and 20 +/- 2 nA per chamber, respectively. and lactate dehydrogenase release was 10 +/- 1 mU per minute. During anoxia, both chemiluminescences dropped to background levels, although lactate dehydrogenase release increased progressively to 38 +/- 7 mU per minute. During reoxygenation, O2 formation increased sharply to 45 +/- 6 nA and decreased to control levels; H2O2 production increased slowly, reaching 42 +/- 7 nA at the end of the reoxygenation period; lactate dehydrogenase declined progressively to control values. These results show that osteoblastlike cells produce measurable amounts of superoxide and hydrogen peroxide radicals during reoxygenation. Because lactate dehydrogenase release did not appear to relate to chemiluminescence, oxyradical flux may serve as a signal for other events that eventually lead to cell injury.     

Dose-dependent character of the effect of hydrocortisone on energy metabolism of rat thymocytes

OBJECTIVES: Pancreatic hypoxia/ischemia, as a consequence of shock-induced microcirculatory failure, is considered a causative factor in the initiation and/or progression of pancreatic tissue injury. The aim of this study was to compare the effects of "small volume resuscitation" with conventional isovolemic colloid and hypervolemic crystalloid resuscitation on pancreatic microcirculation after hemorrhagic shock. DESIGN: Randomized, controlled intervention trial. SETTING: University laboratory. SUBJECTS: Twenty-three male Sprague-Dawley rats anesthetized with á-chloralose mechanically and ventilated. Interventions: Rats subjected to 1 hr of hemorrhagic shock (mean arterial pressure of 40 mm Hg) were resuscitated with lactated Ringer's solution (four-fold shed volume/20 mins), 10% hydroxyethyl starch (shed volume/5 mins), or 7.2% sodium chloride-10% hydroxyethyl starch (10% shed volume/2 mins). MEASUREMENTS AND MAIN RESULTS: The microcirculation of pancreatic acinar tissue was studied by means of intravital fluorescence microscopy and laser Doppler flowmetry. At 1 hr after resuscitation, mean arterial pressure, pancreatic capillary erythrocyte velocity, and erythrocyte flux were found to be significantly increased when compared with those values in the shock state. However, mean arterial pressure, pancreatic capillary erythrocyte velocity, and erythrocyte flux did not completely return to preshock values, regardless of the type of fluid used for resuscitation. At 15 mins and 1 hr after resuscitation, shock-induced capillary perfusion failure (reduction of functional capillary density) was restored to 91% to 94% of baseline values in all groups. Pancreatic capillary narrowing, indicating microvascular endothelial cell swelling, was abolished by resuscitation with both isotonic hydroxyethyl starch and hypertonic hydroxyethyl starch (p<.05 vs. lactated Ringer's solution). CONCLUSIONS: Despite replacement of only 10% of actual blood loss, small-volume resuscitation with hypertonic hydroxyethyl starch is as effective as the ten-fold volume of isotonic hydroxyethyl starch and, due to prevention of microvascular endothelial cell swelling, superior to the 40-fold volume of isotonic lactated Ringer's solution in regard to restoration of the shock-induced microcirculatory disturbances of rat pancreatic acinar tissue.     

Effects of hypertonic sodium lactate dextran resuscitation in severely burned dogs

12 dogs with 35% TBSA third degree burns received HLD resuscitation (HLD group, n = 6) or LR resuscitation (LR group, n = 6). Fluid resuscitation started one hour postburn. The amount of fluid infused with HLD resuscitation was calculated by that after giving HLD 19.6 ml/kg in 3 hours and 6 ml/kg/% TBSA lactate Ringer's solution followed. The amount of fluid infused with LR resuscitation was calculated by 8 ml/kg/% TBSA lactate Ringer's solution. Infusion of lactated Ringer's solution in both groups was adjusted by maintaining urinary output 0.5-1 ml/kg/h. The volume of fluid infused in HLD group (5.05 +/- 1.11 ml/kg/% TBSA) was much less than that of LR group (10.03 +/- 1.30 ml/kg/%TBSA) (P < 0.01). There was no significant difference in urinary output, serum Na+ and albumin, and plasmacrystalloid osmolarity between two groups. Plasma level of MDA decreased after resuscitation with HLD, which (0.81 +/- 0.20 mmol/g Hb) was much lower than that (1.39 +/- 0.44 mmol/g Hb) of LR group 4 hours postburn (P < 0.05). Plasma SOD activity (7.22 +/- 0.68 u/g Hb) of HLD group were much higher than that of LR group (4.86 +/- 0.53 u/g Hb) 4 hours postburn (P < 0.05). HLD resuscitation could significant reduce the amount of fluid infused comparing with lactate Ringer's solution. HLD resuscitation could attenuate postburn damage to tissue induced by lipid peroxide by elevating plasma SOD activity.     

The relationship between the adenine nucleotide metabolism and the conversion of the xanthine oxidase enzyme system in ischemia-reperfusion of the rat small intestine

The time course of the energy metabolism after reperfusion, the relationship between the conversion of xanthine dehydrogenase to xanthine oxidase (D-to-O conversion) during ischemia, and the changes of the energy metabolism after reperfusion were studied using an ischemia-reperfusion model in the small intestine of the rat. The rat jejunum underwent an occlusion of the superior mesenteric artery and vein for either 30 minutes (group 1, n = 6) or 90 minutes (group 2, n = 6) with collateral interruption, and then it was reperfused. The contents of the adenine nucleotides in the small intestine of the rat were measured by high-performance liquid chromatography (HPLC) before ischemia, and 30, 60, and 90 minutes of ischemia, as well as 30, 60, 120, and 180 minutes after reperfusion. The recovery level of adenosine triphosphate (ATP) in group 1 (6.05 +/- 0.80 mumol/g dry weight) 30 minutes after reperfusion was significantly higher than that in group 2 (2.28 +/- 1.12 mumol/g dry weight) (P < .001). In addition, the ATP content after reperfusion in group 2 did not change from 30 to 180 minutes after reperfusion. The D-to-O conversion during ischemia in group 1 was not significantly greater than that before ischemia; however, that of group 2 did increase significantly during ischemia (P < .005). These results suggest that the tissue damage from ischemia-reperfusion injury after reperfusion under 90 minutes' ischemia is accomplished within the first 30 minutes after reperfusion. Therefore, the ATP level at 30 minutes after reperfusion may be useful for the evaluation of intestinal viability. Thus, the conversion of the xanthine oxidase enzyme system might play an important role in the expression of ischemia-reperfusion injury.     

Effect of alpha(alpha)-cross-linked hemoglobin and pyridoxalated hemoglobin polyoxyethylene conjugate solutions on gastrointestinal regional perfusion in hemorrhagic shock

BACKGROUND: Hemoglobin-based blood substitutes may cause vasoconstriction, which could limit organ perfusion during trauma resuscitation. We investigated the effect of two hemoglobin solutions on regional blood flow and mucosal perfusion in the gastrointestinal tract in a hemorrhagic shock model. METHODS: Twenty-four swine were bled 30% of blood volume over 1 hour. Six additional animals were anesthetized and monitored but did not undergo hemorrhage. Bled animals were resuscitated with alpha(alpha)-hemoglobin (alpha(alpha)Hb), pyridoxalated hemoglobin polyoxyethylene conjugate (PHP), shed blood, or lactated Ringer's solution. Regional blood flow was measured by radiolabeled microspheres. Gastric mucosal perfusion was estimated by measuring intramucosal pH (pHi) by tonometry. RESULTS: PHP and shed blood restored small-bowel flows to sham values, whereas lactated Ringer's solution and alpha(alpha)Hb did not. Shed blood and PHP, but not alpha(alpha)Hb, restored cardiac index (CI) to baseline (p < 0.05). Mean pulmonary artery pressure was elevated over baseline with alpha(alpha)Hb and PHP and remained elevated with alpha(alpha)Hb (p < 0.05). pHi was significantly lower after resuscitation with PHP than with other fluids. CONCLUSION: PHP was efficacious in restoring CI and small-bowel flow, but the pHi remained low, indicating possible continued mucosal ischemia. Alpha(alpha)Hb led to limited recovery of CI and small-bowel blood flow but restored pHi close to baseline. Shed blood was efficacious in restoration of pHi, gastrointestinal blood flows, and systemic hemodynamics.     

Effect of glutathione depletion on the conversion of xanthine dehydrogenase to oxidase in rat liver

The ability of endogenous glutathione (GSH) to modify the activity of the enzyme xanthine oxidase (XO) in rat liver was investigated. The effect of hepatic GSH depletion on the conversion of xanthine dehydrogenase (XDH) (EC 1.1.1.204) to XO (EC 1.1.3.22) was determined 10 min after i.p. administration of different amounts of diethylmaleate to fasted rats. After administration of 400 mg/kg, total hepatic non-protein GSH (reduced + oxidized GSH) decreased significantly to 14% of controls. In this condition the level of oxidized GSH was unchanged and no lipid peroxidation was observed, while a significant increase of reversible XO and a minor increase of the irreversible form of the enzyme was detected.     

Morphological and chromosomal descriptions of new species in the Anopheles subpictus complex

In the present work, the role of lipid peroxidation in cellular lethal injury induced by various types of oxidative stress has been studied in both normal and tumor thymocytes. The prooxidants included either a xanthine/xanthine oxidase system, which is an exogenous source of oxyradicals, or tert-butyl hydroperoxide (t-BOOH), which enters the cell and endogenously produces free radicals. Our data demonstrate that: (A) Using xanthine/xanthine oxidase system as a prooxidant, normal thymocytes are more sensitive than thymoma cells to oxidative damage, as their lactate dehydrogenase (LDH) and malondialdehyde (MDA) release is higher than that of tumor cells. By varying Fe3+/ADP ratios, a positive correlation can be established between LDH and MDA release only in normal thymocytes. While thymoma cells still show a very high level of vitamin E (80%) after 15 min of incubation with this prooxidant, normal thymocytes lose it after the same incubation time. (B) Using t-BOOH as a prooxidant, normal thymocytes release a higher amount of MDA but a lower amount of LDH than thymoma cells. In agreement with the results obtained with the xanthine/xanthine oxidase system, by varying the concentrations of the prooxidant, a correlation between LDH and MDA release can be established only in normal thymocytes. Although high levels of the antioxidant are still present in both kinds of cells after 15 min of incubation with t-BOOH, normal thymocytes consume vitamin E faster than thymoma cells. These data suggest that the role of lipid peroxidation in cell lethal injury is influenced by the source and the site of radical production as well as by the cell type. With t-BOOH as a prooxidant in normal thymocytes, lipid peroxidation is only partially involved in the induction of irreversible cell injury, but it plays a crucial role when the xanthine/xanthine oxidase system is used as a prooxidant. Moreover, whatever the prooxidant used in tumor thymocytes, membranes are more resistant to lipid peroxidation, suggesting that this mechanism is not causally related to cell death.     

Uncontrolled hemorrhage from parenchymal injury: is resuscitation helpful?

Fluid resuscitation increases blood pressure and may increase hemorrhage. We tested this hypothesis in a model of liver injury. After standardized injury, rats were randomized into four groups: no resuscitation (NR, n = 30), small volume lactated Ringer's solution (SVLR, 4 mL/kg, n = 30), large volume lactated Ringer's solution (LVLR, 24 mL/kg, n = 30), and hypertonic saline (HS, 4 mL/kg, n = 30). Terminal circulating volume was estimated using controlled hemorrhage experiments. Survival times and mortality rates were significantly lower in HS animals (10%) than in NR (50%) or SVLR (47%) animals. Blood pressure was significantly higher after HS, and this difference was sustained. Intraperitoneal blood volume was significantly higher with HS (26.0 +/- 0.7 mL/kg) and LVLR (26.9 +/- 0.6 mL/kg) compared with NR (21.5 +/- 0.7 mL/kg) and SVLR (22.5 +/- 0.7 mL/kg). Estimated terminal blood volume was significantly decreased in LVLR (29.3 +/- 0.6 mL/kg) compared with NR (33.3 +/- 0.7 mL/kg), SVLR (33.7 +/- 0.8 mL/kg), and HS (31.7 +/- 0.7 mL/kg). CONCLUSION: Vigorous resuscitation increases bleeding from solid viscus injury. Small volume HS improves blood pressure and survival compared with no resuscitation. Results of large vessel hemorrhage models may not apply to parenchymal viscus injury.     

Role of xanthine oxidase-derived oxidants and leukocytes in ethanol-induced jejunal mucosal injury

Previous reports indicate that intestinal intraluminal ethanol increases mucosal permeability (an index of mucosal injury) and histamine release by mast cells, and that the released histamine plays a role in mediating the increased permeability. In the present study, we investigated whether reactive oxygen metabolites and their major sources (xanthine oxidase and leukocytes) were involved in these ethanol effects. In rabbits, segments of the jejunum were perfused with a control solution or with 6% ethanol. In these segments, mucosal permeability was assessed by determining jejunal clearance of i.v. administered 51Cr-ethylenediaminetetraacetate (51Cr-EDTA) and 125I-bovine serum albumin (125I-BSA), and mast cell histamine release was estimated from the histamine concentration of the gut effluent. Ethanol increased 51Cr-EDTA clearance, 125I-BSA clearance, and histamine release. These ethanol effects decreased when the animals were given superoxide dismutase plus catalase (scavenger of O2- and H2O2, respectively), allopurinol, or oxypurinol (xanthine oxidase inhibitors). Administration of a monoclonal antibody (R15.7) against leukocyte adhesion molecule, CD18, inhibited completely the ethanol-induced increased 51Cr-EDTA and 125I-BSA clearances and histamine release. These and supplementary data suggest that (a) ethanol-induced mucosal injury and mast cell histamine release are mediated primarily by leukocytes, and (b) oxy radicals, especially those generated by xanthine oxidase, mediate these ethanol effects mainly by promoting leukocyte infiltration.     

Hypertonic saline dextran prime reduces increased intracranial pressure during cardiopulmonary bypass in pigs

Children and adults who develop neurologic deficits after cardiac surgery may experience cerebral ischemia during cardiopulmonary bypass. Increased intracranial pressure (ICP) may contribute to cerebral ischemia during bypass. Hypertonic saline dextran (HSD), a hyperosmotic, hyperoncotic resuscitation solution, decreases ICP in trauma resuscitation. We hypothesized that HSD would decrease ICP, reduce brain water, and reduce intravascular fluid requirements during bypass. Twelve swine were divided into two bypass groups: Group 1 (ISO = isotonic) received as prime 1 L of lactated Ringer's solution and 500 mL of 6% hydroxyethyl starch. Group 2 (HSD = hypertonic saline/dextran) received as prime 1 L of lactated Ringer's solution, 500 mL of 6% hydroxyethyl starch, and 1 mL/kg of 24% hypertonic saline/25% dextran. Normothermic bypass was instituted at 100 mL.kg-1.min-1. ICP increased significantly during bypass with ISO prime but not with HSD. Brain water in the cerebrum did not differ between groups but was reduced in the cerebellum to 75.9% +/- 1.4%. We conclude that HSD prevented any significant increase in ICP during normothermic bypass, and substantially improved fluid balance during bypass. In cardiac surgery patients in whom maintaining decreased ICP and reducing isotonic fluid administration is important, HSD may be a useful addition to the bypass prime solution.