Allopurinol prevents intestinal permeability changes after ischemia-reperfusion injury.

Under normal conditions the intestinal mucosa is impermeable to potentially harmful materials from the intestinal lumen. Mucosal disruption promotes bacterial translocation, which is postulated to be a fuel source for sepsis and multiorgan failure. We have previously demonstrated that mesenteric ischemia-reperfusion (I/R) injury increases intestinal permeability (IP); however, the mechanism remains unclear. This study was designed to examine the hypothesis that changes in IP, after I/R injury, are mediated by xanthine oxidase-generated, oxygen-derived free radicals. Thirty-three Sprague-Dawley rats (weighing 300 to 400 g) were included in this study. Group 1 (n = 10) received enteral allopurinol, a xanthine oxidase inhibitor, 10 mg/kg daily for 1 week prior to mesenteric ischemia. Group 2 consisted of 11 untreated, ischemic animals. Groups 1 and 2 were subjected to superior mesenteric artery occlusion with interruption of collateral flow for 20 minutes to produce ischemic injury to the intestine. An additional 12 rats (group 3), served as nonischemic controls (sham). A loop of distal ileum was isolated and cannulated proximally and distally to allow luminal perfusion with warmed Ringer's lactate at 1 mL/min. IP was determined in all groups by quantitatively measuring the plasma-to-luminal clearance of chromium (51Cr)-labeled ethylenediaminetetraacetate (EDTA) at baseline, during ischemia and 20, 40, and 60 minutes after reperfusion. Complete ischemia produced significant increases in IP over baseline values in the untreated rats (group 2, baseline: 0.49 +/- 0.006, ischemia: 0.149 +/- 0.039) compared with sham rats (baseline: 0.41 +/- 0.006; ischemia: 0.047 +/- 0.009) or allopurinol-treated rats (baseline: 0.098 +/- 0.020, ischemia: 0.073 +/- 0.012, P less than .001).(ABSTRACT TRUNCATED AT 250 WORDS)     

Alterations in hypothalamic function following thermal injury.

Nine burn patients with a mean burn size of 39% (range, 23-65%) and five normal individuals studied in an environmental chamber selected optimal comfort temperature by regulating a bedside temperature control unit. The normal individuals selected 27.8 degrees C plus or minus 0.6 (SE) as the comfort temperature and their mean skin temperature was 33.4 plus or minus 0.6 and core temperature 36.9 plus or minus 0.1 while in this environment. In contrast, the burn patients maintained a higher ambient comfort temperature (mean 30.4 plus or minus 0.7, p less than 0.05 when compared to controls) associated with an elevated core (38.4 plus or minus 0.3, p less than 0.01) and surface temperature (35.2 plus or minus 0.4, p less than 0.05). Human growth hormone response to insulin hypoglycemia and arginine infusion was measured in nine additional burn patients (mean burn size, 52%; range, 23-90%) and five normals. Fasting HGH was significantly elevated (1.7 plus or minus 0.2 ng/ml, n = 18, versus control of 0.9 plus or minus 0.1, n = 10, p less than 0.001), despite fasting hyperglycemia in the burn patients (123 plus or minus 5 mg/100 glycemia in the burn patients (123 plus or minus 5 mg/100 ml versus 91 plus or minus 2, p less than 0.001). HGH response to insulin hypoglycemia was diminished in the burn patients with peak HGH value in patients averaging 12.6 ng/ml compared to 27.8 in the recovered patients and 32.6 in the controls (p less than 0.01). Patients receiving an arginine infusion also demonstrated diminished HGH response following injury. The HGH response to known stimuli returned toward normal with time and recovery in the surviving patients. Alterations in comfort temperature, fasting blood glucose, and glucose-HGH interaction occur following thermal trauma. These changes taken together suggest that metabolic responses to injury may be the consequence of homeostatic readjustment within the hypothalamus.     

Increased transcellular permeability of rat small intestine after thermal injury.

The pathway which results in a loss of intestinal barrier function and transepithelial transfer of macromolecules after cutaneous thermal injury is unknown. To determine the enhanced absorption pathway, transepithelial transport of horseradish peroxidase (HRP) was examined ultrastructurally after a thermal injury. Within 6 h after the injury, increased HRP uptake was seen in the portal and systemic blood with the maximal increase in uptake measured at 18 h postinjury; permeability returned to normal by 72 h postinjury. Morphologically, the increased uptake was found to be transcellular through ultrastructurally normal intestinal absorptive cells. Occasional focal regions of enhanced HRP uptake were found and this enhanced uptake was attributed to focal intestinal epithelial disruptions. This increase in intestinal permeability represents a transient loss of intestinal barrier function and potentially allows absorption of macromolecules such as endotoxin from the intestinal lumen into the portal circulation early after thermal injury.     

The effects of thermal injury on transcellular permeability and intestinal P-glycoprotein in rats

This study was designed to assess intestinal drug transport via transcellular absorption and intestinal P-glycoprotein content following thermal injury in rats using propranolol as a marker substrate. Male, Sprague Dawley rats (n=30) underwent either a 30% total body surface area full thickness burn or sham treatment. Twenty-four hours later, animals were anesthetized, underwent laparotomy and the proximal jejunum was cannulated. The jejunal segment was perfused with buffer containing [³H] propranolol. Following euthanasia, jejunal tissue was harvested for Western immunoblotting of P-glycoprotein and villin, and immunohistochemical analysis of P-glycoprotein. Dramatic structural changes in jejunal integrity were observed following thermal injury; however, no significant differences in the absorption characteristics of propranolol following thermal injury were observed. Mean effective permeability of propranolol was 5.67±1.79 and 5.85±1.67 cm/s×10⁻⁵ for burn and sham groups, respectively (P>0.05). P-glycoprotein and villin content in the jejunum were significantly decreased in burn animals. The transcellular transport of propranolol is unaffected 24 h following thermal injury in rats, despite alterations in intestinal P-glycoprotein content. The decrease in P-glycoprotein and villin content in thermally injured animals may reflect loss of mature enterocytes at the villus tips.     

Analysis of altered capillary pressure and permeability after thermal injury

In order to investigate the effects of thermal injury on microvascular hemodynamics and permeability, hindpaw arterial (PA), venous (PV), and capillary (PC) pressures, blood (QB) and lymph (QL) flows, and lymph (CL) and plasma (CP) total protein concentrations were measured before and for 3 hr after a 10-sec 100 degrees C scald burn in 11 dogs. Prior to injury in eight experiments (Group I--permeability analysis) venous pressure was elevated by outflow restriction until the minimal CL/CP was obtained. In three experiments (Group II--hemodynamic analysis) outflow was not restricted. Lymph and plasma protein fractions ranging in size from 37 to 120 A were measured using gradient gel electrophoresis and capillary equivalent pore sizes were calculated. In the early postburn period, PC increased from 24 +/- 2 (mean +/- SE) to 47 +/- 5 mm Hg (P less than 0.05) and precapillary resistance (RA) decreased from 6.6 +/- 0.2 to 2.5 +/- 0.2 mm Hg/ml/min/100 g (P less than 0.05) while postcapillary resistance (RV) remained unchanged. Pre- to postcapillary resistance (RA/RV) fell by 74%. The reflection coefficient for total proteins (calculated as sigma = 1 - CL/CP) decreased from 0.87 +/- 0.01 to 0.45 +/- 0.02 (P less than 0.01). Permeability of the postburn capillary endothelium was described by using two populations of equivalent pores. Preburn pore radii were 50 and 300 A with 13% of the capillary filtrate passing through the large pores. Pore radii increased after injury to 70 and 400 A with 49% of the filtrate passing through the large pores. The postburn total tissue filtration coefficient (Kf) increased to 2.4 times the control. Over the first 3 hr postburn, 53% of the increase in capillary filtration was attributable to increased capillary pressure and 47% to increased permeability. We conclude that the early rapid edema formation following thermal injury is the result of marked increases in both capillary filtration pressure and filtration through large nonsieving pores.     

Increased mucosal permeability after intestinal ischemia-reperfusion injury is mediated by local tissue factors.

Subclinical intestinal ischemia-reperfusion injury (IRI) causes an increase in mucosal permeability and may represent an early event in the pathogenesis of necrotizing enterocolitis. The present study was undertaken to determine whether these changes are mediated by local or systemic factors. In 6-week-old weanling rats, the ileum was divided into two isolated loops with separate vascular supplies. The mesentery of the proximal loop was occluded for 30 minutes, following which the bowel was reperfused; permeability to 51Cr EDTA was then assessed in the distal loop 30 minutes after reperfusion. In control groups, the distal loop was subjected to 30-minute IRI ("positive" control) or 30-minute sham operation ("negative" control). Permeability in the distal loop was increased only with IRI to the distal bowel (15.4 +/- 3 counts/min/standard), and not with IRI to the proximal bowel (5.1 +/- 1) or with sham operation (8.5 +/- 2). To determine whether a mild "priming" injury might be necessary for systemic factors to have an effect, the distal loop was subjected to 2-minute IRI and the proximal to 30-minute IRI or sham. Permeability was not increased in the distal loop in either of these groups (5.7 +/- 1 and 7.8 +/- 2, respectively). Thirty-minute IRI in the proximal loop did not increase permeability in the distal loop, with or without a priming injury. Only direct IRI in the distal loop resulted in a significant increase in permeability. We conclude that the permeability changes in this model are mediated through local tissue effects, rather than by systemic factors.     

Bacterial translocation and intestinal atrophy after thermal injury and burn wound sepsis.

Bacterial translocation (BT) occurs after thermal injury in rodents in association with intestinal barrier loss. Infection complicating thermal injury may also affect the intestine producing bowel atrophy. To study these relationships, Wistar rats received either 30% scald followed by wound inoculation with Pseudomonas; 30% scald with pair feeding to infected animals; or sham injury as controls. On days 1, 4, and 7 after injury animals were killed with examination of the bowel and culture of the mesenteric lymph nodes (MLN), livers, spleens, and blood. All burned animals demonstrated BT to the MLN on day 1 after injury, but only burn-infected animals had continued BT on days 4 and 7, with progression of BT to the abdominal organs and blood. Burn injury and infection also resulted in significant atrophy of small bowel mucosa temporally associated with continued BT. Thus injury complicated by infection results in prolonged and enhanced bacterial translocation, perhaps due to failure to maintain the mucosal barrier.     

烧伤后肠上皮通透性变化机制和对策

After a series of studies, we found that the intestinal permeability was increased, tight junction protein (zonula occluden-1 ) obviously decreased and redistributed, accompanied by an increase in expression of myosin light chain (MLC) phosphorylation in severely burned rats. After using inhibitor of MLC kinase ( ML-9 2mg/kg) or of Rho-associated kinase (Y-27632 2mg/kg), above-mentioned changes could be alleviated. Therefore, to regulate the MLC phosphorylation of tight junction protein and perijunctional actin-myosin ring may be one of the key links to lessen the intestinal epithelium permeability after burn injury.     

Differential alterations in intestinal permeability after trauma-hemorrhage

BACKGROUND: Recent studies have shown that the intestinal barrier function is altered and macromolecules can translocate after trauma and hemorrhagic shock. The translocated molecules are absorbed from the lymphatic tissue or directly enter the circulation in the gut. However, it remains unknown to what degree these compartments contribute to the clearance of the macromolecules. METHODS: Male Sprague-Dawley rats (350-400 g) underwent a 5-cm midline laparotomy (i.e., soft tissue injury), were bled to a mean arterial pressure of 35 mmHg and maintained for approximately 90 min, and then resuscitated with Ringer's lactate (4x the shed blood volume) over 60 min. At 2 h after resuscitation, a solution containing 51Cr-EDTA, FITC-dextran-4 kDa, and rhodamine B-dextran-40 kDa was instilled into a jejunal blind loop and their concentrations were determined in mesenteric lymph and blood samples harvested between 2 h and 4 h after resuscitation. RESULTS: Trauma-hemorrhage and crystalloid resuscitation significantly increased mesenteric lymph flow and the mucosal permeability for the three marker molecules. There was no difference in the concentrations of 51Cr-EDTA between the blood and lymph compartment after trauma-hemorrhage. However, the high molecular weight marker (rhodamine-B-dextran-40 kDa) accumulated in significantly higher concentrations in the mesenteric lymph than in the plasma under such conditions. CONCLUSIONS: The accumulation of macromolecules in the mesenteric lymph suggests that this compartment plays an important role in the altered gut barrier function after trauma-hemorrhage.     

Importance of increased intestinal permeability after multiple injuries.

OBJECTIVE: To find out if there was a relationship between increased intestinal permeability and the development of multiple organ failure (MOF) after multiple injuries, we correlated the extent of injury and MOF with intestinal permeability on the second and fourth day after injury. DESIGN: Prospective open study. SETTING: University hospital, Slovenia. PATIENTS: 29 multiply injured patients, injury severity score (ISS) over 25, admitted shocked. INTERVENTION: Intestinal permeability measured by giving lactulose and mannitol solution enterally on days 2 and 4. MAIN OUTCOME MEASURES: The lactulose: mannitol ratio calculated from the urinary portion of the probe molecules. ISS and the acute physiology and chronic health evaluation (APACHE II) calculated on admission. RESULTS: The median lactulose: mannitol ratio for five volunteers was 0.014 (range 0.008-0.017) and that for 29 patients was 0.03 (0.01-0.1). On day 2 it was 0.03 (0.02-0.1), on day 4 0.02 (0.01-0.2). The ratio calculated on day 2 correlated with average and late MOF scores (r = 0.41 R2 = 0.1681, p <0.03 and r = 0.38, R2 = 0.1444, p <0.04) and that measured on day 4 correlated with overall, early, and late MOF scores (r = 0.47, R2 = 0.2209, p <0.01; r = 0.51, R2 = 0.2601, p <0.005; r = 0.39, R = 0.1512, p <0.04). No correlation was found between ISS, transport time, shock index, APACHE II, and days in intensive care. CONCLUSIONS: Even if intestinal permeability is invariably increased after injury, it seems to have some predictive value for MOF in multiply injured patients because it correlates with its development.     

Granulocyte oxidative activity after thermal injury.

BACKGROUND. Alterations in granulocyte function after thermal injury have been described. We have serially studied the level of granulocyte cytosolic peroxidase activity in 23 thermally injured patients during the first 6 weeks after injury. The patients' mean age and burn size were 35.1 +/- 15.7 years and 41.6% +/- 16.8% (range, 18% to 88%), respectively. Fourteen patients had concomitant inhalation injury, and the overall mortality rate was 4.3%. METHODS. Purified granulocytes were obtained from peripheral blood after red cell lysis and Ficoll-Hypaque (Pharmacia Inc., Piscataway, N.J.) gradient separation. Cells were loaded with dichlorofluorescin diacetate, and baseline fluorescence was measured by flow cytometry. After phorbol myristate acetate stimulation, fluorescence was measured again. Cells from unburned normal subjects were used as daily controls. RESULTS. The data are expressed as percent of stimulated control granulocyte fluorescence. Unstimulated patient granulocytes demonstrated a significantly higher baseline activity than did unstimulated controls (22.9% vs 15.4%; p < 0.05). Mean fluorescence from stimulated granulocytes was 114% of the control values (p < 0.05). CONCLUSIONS. Granulocytes from thermally injured patients exhibited a baseline increase in cytosolic oxidase activity, suggesting in vivo activation and a greater than normal oxidase activity after in vitro stimulation.     

Normoblastemia after thermal injury

The peripheral blood smears of 214 thermally injured patients studied during a thirty month period revealed a 20 per cent incidence of normoblastemia (51 patients). Nucleated red blood cells were most common in patients with the largest burns. The absolute number of normoblasts was not related to the hematocrit and was not correlated with other determinants of erythropoietic function.     

Lymphoid subpopulation changes after thermal injury and thermal injury with infection in an experimental model.

Subpopulation analysis of peripheral blood lymphocytes is a frequently used measure of immunocompetence. Yet, little is known about the lymphocyte subpopulations in the circulation and lymphoid organs after severe trauma. Blood, spleen, and lymph node (LN) subpopulations were compared in a rat model of burn injury (B) and burn injury with infection (BI). B and BI rats received 30% total body surface scald burns. Infection was induced by seeding wounds with Pseudomonas aeruginosa. Subpopulations were identified by flow cytometry 48 hours after burn. Helper lymphocytes were selectively depleted from the circulation of BI but not B animals, which caused the ratio of helper to suppressor cells (HSR) in BI animals to decrease significantly compared with the unburned controls. Both LN helper and suppressor cells were decreased in BI animals and the HSR was unchanged, but a selective reduction in suppressor cells in B LN increased the HSR relative to unburned controls. Spleen subpopulations were unchanged for both B and BI groups. Subpopulation changes after trauma and infection were different for each tissue examined.     

Acute liver disease after cutaneous thermal injury.

To better define the acute liver disease complicating thermal injury, 81 burn patients were evaluated for hepatic damage. Clinical and laboratory evidence of hepatocellular injury was present as early as 24 hours after burn in 47 patients (58%). Patients with liver disease had a larger mean burn size (p less than 0.01) and greater mortality than patients with normal liver studies. The magnitude of initial enzyme derangements did not distinguish the survivors, but jaundice was associated with a poor prognosis. Seventeen of the 19 jaundiced patients (90%) died. The early occurrence of hepatocellular injury suggested that acute hemodynamic alterations were important etiologically. Intrahepatic cholestasis and jaundice developed later in septic or hypoxic patients and was accentuated by hemolysis and blood transfusions. In these patients, liver histology showed a nonspecific hepatitis. An increased risk of septic complications could not be attributed to the presence of liver disease. Late emergence of conjugated hyperbilirubinemia suggested an underlying septic process.     

Alterations in bile following urinary intestinal diversion.

In order to determine whether alterations in bile occur which make it more lithogenic when intestinal segments are interposed in the urinary tract, 42 female Sprague-Dawley rats had intestinal and urointestinal manipulations followed by analysis of bile constituents. Timed collections were obtained from the common bile duct which were analyzed for bile acids, phospholipids, cholesterol, bilirubin, volume, osmolality, pH, calcium, chloride, sodium, and potassium. Changes in bile constituents were identified following urinary diversion which were specific for the type of diversion and the segment of bowel used, but they were not of sufficient degree to cause significant changes in the lithogenicity of bile. This correlates well with the lack of clinical findings of cholelithiasis in children with urinary intestinal diversion.     

Peripheral vascular permeability following a thermal injury to the airway

Effects of thermal injury to the airway on the vascular permeability in the region of head and neck, were studied in the canine models. The thermal airway injury was produced by an inhalation of a gas burners flame through the metallic tracheostomy cannula. The changes in vascular permeability were evaluated by calculating the reflection coefficient, which was obtained by the protein washdown technique into lymph. The reflection coefficient after the flame inhalation did not show any increases, while it increased significantly after a histamine infusion into the carotic artery. We concluded, that the vascular permeability in the unburned area does not increase at least in the first 3hr after a thermal injury to the airway.(Okamoto K, Noguchi H, Akashi M, et al.: Peripheral vascular permeability following a thermal injury to the airway. J Anesth 5: 79–87, 1991)