Glutamine metabolism by the endotoxin-injured lung.

The alterations in lung glutamine (GLN) metabolism that occurs in the endotoxin-injured lung were studied in rats and subsequently correlated with flux changes that occur in patients with the adult respiratory distress syndrome (ARDS). Measurements in animals were made at various time-points following the administration of endotoxin, while studies in surgical patients were done in a group of healthy controls, in patients with "early" sepsis who had normal chest x-ray films, and in patients with radiographic and physiologic evidence of ARDS. In healthy control rats, net amounts of GLN are released by the lungs into the systemic circulation. This release rate doubled 30 minutes after intravenous endotoxin (1,580 +/- 320 nmol GLN/100 g BW/min vs. 736 +/- 179 in controls, p less than 0.01) but glutamine synthetase activity was unchanged, suggesting an outpouring of cellular glutamine stores. Two hours after endotoxin treatment, this accelerated fractional release of glutamine by the lungs was no longer detected. By the 12-hour time-point, the lungs reversed to an organ of net glutamine balance (234 +/- 248 nmol/100 g BW/min, p less than 0.05 vs. controls and ENDO30 min) despite a more than two-fold increase in glutamine synthetase activity (p less than 0.01). Simultaneously, lung weights were increased by 21% (p less than 0.01) and histologic examination showed an interstitial infiltrate and pulmonary edema. Similar observations were made in humans; patients with "early" sepsis exhibited a marked increase in lung glutamine release, while patients with ARDS demonstrated glutamine balance across the lungs (4,030 +/- 910 nmol GLN/kg BW/min vs. 637 +/- 496 in ARDS, p less than 0.05).(ABSTRACT TRUNCATED AT 250 WORDS)     

Glutamine-containing dipeptides as infusion substrates in the septic state

Recently a relationship has been postulated between lowered intracellular glutamine concentrations in the skeletal muscle and the rate of protein synthesis. We investigated the effect of 48 hours of parenteral nutrition supplemented with a solution containing glutamine in free or dipeptide form (alanylglutamine or glycylglutamine) on the intracellular glutamine pool in skeletal muscle and on the hind limb exchange of glutamine in dogs with sepsis after surgery. Before surgery, dogs were fasted for 48 hours. We used glutamine dipeptides as sources because they remain stable in an aqueous solution. Nutrition solutions were isocaloric (17.8 kcal/kg body weight/day on day 1 and 35.6 kcal/kg on day 2) and isonitrogenous (0.33 gm nitrogen/kg body weight/day), providing 2.6 mmol/kg body weight/day as glutamine source. During starvation, muscular free glutamine levels decreased by 41% to 10.4 mmol/L (p less than 0.001). On the second postoperative day the dogs had lowered plasma protein levels, a sharp drop in platelet count, an increase in the leukocyte count, and positive blood cultures. None of the solutions investigated in this study was effective in repleting the glutamine pool during 2 days of postoperative nutrition (11 +/- 2.0 mmol/L without glutamine, 10.3 +/- 2.2 mmol/L with glutamine plus alanine, 9.9 +/- 1.6 mmol/L with alanylglutamine, 7.5 +/- 1.1 mmol/L with glutamine plus glycine, and 7.2 +/- 1.2 mmol/L with glycylglutamine, respectively). The release of glutamine from the hindquarter was 631 +/- 38 nmol/kg body weight/min in the control group and decreased significantly in dogs receiving alanylglutamine (13.5 +/- 45 nmol/kg body weight/min; p less than 0.001) or the constituent amino acids (265 +/- 66 nmol/kg body weight/min; p less than 0.01) but was unchanged in dogs receiving glycylglutamine or glutamine plus glycine. We conclude that the duration and dosage of glutamine administration (equivalent to 26 gm glutamine per day in a patient weighing 70 kg) used in this study are not sufficient to restore glutamine deficiency of the skeletal muscle in the depleted state.     

The effect of graded doses of insulin on peripheral glucose uptake and lactate release in cancer cachexia

With the euglycemic clamp technique, we evaluated the effects of graded doses of insulin on glucose turnover rates and forearm lactate balance in five weight-losing patients with cancer before surgery and five age- and weight-matched healthy volunteers (control subjects). Insulin was infused sequentially at increasing rates of 0.5 (low physiologic), 1.0 (high physiologic), and 4.0 (supraphysiologic) mU/kg.min for 120 minutes each. Concurrently, rates of glucose appearance and disappearance were derived from [3-3H] glucose infusion. The mean postabsorptive rate of glucose appearance in patients (2.9 +/- 0.1 mg/kg.min) was significantly higher (p less than 0.02) than that of control subjects (1.98 +/- 0.16 mg/kg.min). Complete suppression of endogenous glucose production occurred at high physiologic insulin concentrations. With progressive insulin infusion, the rate of glucose disappearance increased to 3.6 +/- 1.2, 8.7 +/- 0.8, and 13.7 +/- 1.1 mg/kg/min in control subjects and 2.9 +/- 0.4, 5.3 +/- 0.3, and 10.9 +/- 0.9 mg/kg.min in patients, significantly different from that of control subjects (p less than 0.05) during the intermediate (high physiologic) insulin infusion. A comparable slight increase in arterial plasma lactate concentration was observed in both groups with progressive hyperinsulinemia. Baseline peripheral lactate flux was identical in patients (-272 +/- 56 nmol/100 gm.min) and in controls (-271 +/- 57 nmol/100 gm.min). Progressive physiologic hyperinsulinemia resulted in significantly (p less than 0.05) augmented peripheral lactate efflux in patients (-824 +/- 181 nmol/100 gm.min) compared with control subjects (-287 +/- 64 nmol/100 gm.min). Supraphysiologic insulin abolished this increased lactate efflux in patients. Postabsorptive rates of endogenous glucose appearance in weight-losing patients with cancer were elevated, but complete suppression was achieved with insulin concentrations in the physiologic range. Total body glucose use was diminished in these patients, consistent with a state of insulin resistance. This impaired insulin action on peripheral glucose use was associated with an increase in peripheral lactate release in patients.     

Accelerated lung amino acid release in hyperdynamic septic surgical patients

Amino acid flux across the lungs was studied in humans to gain further insight into the altered nitrogen metabolism that characterizes catabolic disease states. Lung flux of glutamine, glutamate, and alanine was determined in three groups of surgical patients with indwelling pulmonary artery catheters: (1) preoperative controls (n = 14), (2) postoperative elective general surgical patients (n = 10, and (3) hyperdynamic septic surgical patients (n = 17). In controls the lung was an organ of amino acid balance. These exchange rates did not change in general surgical patients. In the septic group, glutamine release by the lung increased markedly from a control value of 0.80 +/- 0.99 mumol/kg per minute to 6.80 +/- 1.32 mumol/kg per minute. This accelerated release rate was secondary to both an increase in total pulmonary blood flow and an increase in the pulmonary artery-systemic arterial concentration difference. The lung also became an organ of significant alanine release in septic patients. The lung plays an active metabolic role in the processing of amino acids and may be a key regulator in interorgan nitrogen flux after major injury and infection.     

Endotoxin and renal glutamine metabolism.

The effect of endotoxin on renal glutamine metabolism and ammoniagenesis was investigated in vivo in the rat to gain further insight into the altered glutamine flow that characterizes critical illness. Studies were done 15 hours following a single dose of Escherichia coli lipopolysaccharide (10 mg/kg). Renal blood flow and arterial glutamine concentration were similar in control and study rats, but the kidney switched from an organ of slight glutamine uptake in controls (129 +/- 52 nmol/100 g of body weight per minute) to net release in the endotoxin-treated animals (-273 +/- 170 nmol/100 g of body weight per minute). Simultaneously, the specific activity of renal glutamine synthetase increased by almost 50% (374 +/- 40 nmol/mg of protein per hour in rats given endotoxin vs 253 +/- 12 nmol/mg of protein per hour in controls), while glutaminase was unchanged. Urinary ammonia excretion was reduced by 35% in the endotoxin-treated animals (47 +/- 6 mumol/12 h in endotoxin-treated animals vs 70 +/- 8 mumol/12 h in controls) despite a 10% fall in the arterial bicarbonate value. Endotoxin alters the net flux of glutamine across the kidney which appears to be partially regulated enzymatically. This may impair the kidneys' ability to maintain acid/base homeostasis.     

Insulin stimulates branched chain amino acid uptake and diminishes nitrogen flux from skeletal muscle of injured patients

Resistance to insulin-mediated glucose disposal occurs in uninjured skeletal muscle of trauma patients but the effect of insulin on the accelerated proteolysis of trauma is unknown. We examined the influence of insulin on forearm amino acid and substrate exchange in five normals and four trauma patients using the hyperinsulinemic glucose clamp technique. Forearm substrate and amino acid flux (Q, nM/100 ml tissue/min), the product of blood flow and arterial deep venous concentration difference, was calculated before and during insulin infusion. Total nitrogen release (NQ, nM/100 ml tissue/min) was calculated as the algebraic sum of all nitrogen groups contained in the amino acids released. Among normal subjects, total nitrogen release from the forearm did not change (581 +/- 197 nM/100 ml tissue/min to 1167 +/- 455) during insulin infusion nor did total branched chain amino acid flux (0 +/- 30 nM/100 ml/min to 106 +/- 36). Under conditions of hyperinsulinemia, neither glutamine nor alanine changed in control subjects. In trauma patients, total nitrogen release (3843 +/- 1383 nM/100 ml/min) was inhibited during insulin administration (819 +/- 314, P less than 0.05). Total branched chain amino acid flux went from a net release of 460 +/- 134 nM/100 ml/min to a net uptake of 10 +/- 82 (P less than 0.05). In patients, statistically significant (P less than 0.05) differences were seen in individual amino acids as well. Forearm nitrogen flux was directly related to total branched chain amino acid flux in patients (r2 = 0.89). Additional studies in normals (n = 4) at higher insulin infusion rates confirmed that these effects were unique to injured subjects and not an effect of the insulin dose. Insulin attenuates the accelerated release of skeletal muscle amino acid in trauma patients. This effect may be mediated in part by facilitated branched chain amino acid uptake. The manipulation of both insulin and branched chain amino acid concentrations may provide a method to reduce post-traumatic protein catabolism.     

Increased peripheral amino acid release following burn injury.

Turnover rates of 10 amino acids were determined in four normal subjects and 18 burned patients (mean burn size, 41% of total body surface) by measuring leg blood flow by venous occlusion plethysmography and arterial (A) and femoral venous (FV) amino acid concentrations. Patient arterial plasma amino acid concentrations generally were low or normal, although phenylalanine was elevated. Only alanine demonstrated significant A-FV concentration difference (-9 +/- 2 mumole/100 ml in patients vs -5 +/- 1in controls, mean +/- SEM). Leg blood flow was 6.26 +/- 0.57 ml/100 ml of leg volume . min in the patients and 2.62 +/- 0.57 in controls. While the net peripheral release of the 10 amino acids was accelerated following injury, only alanine release was consistently greater in the patients (0.27 plus or minus 0.05 mumole/100 ml in leg volume . min) as compared with that of controls (0.08 +/- 0.02). The increased alanine release from legs of patients generally was related to the extent of total body surface injury and oxygen consumption of the patient, but was unrelated to size of limb burn or leg blood flow. The accelerated rate of alanine release from limbs of burn patients relates to the generalized catabolic effects of injury rather than to local inflammatory or metabolic events which may occur in the injured extremity.     

Growth hormone after abdominal surgery attenuated forearm glutamine, alanine, 3-methylhistidine, and total amino acid efflux in patients receiving total parenteral nutrition.

OBJECTIVE: The study clarified the effects of growth hormone treatment on forearm amino acid efflux in patients with full nutritional support after gastrointestinal surgery. SUMMARY BACKGROUND DATA: Growth hormone attenuates net nitrogen loss after surgical trauma. An increase in net protein synthesis has been described, whereas the results regarding protein breakdown have been conflicting. METHODS: Elective patients undergoing abdominal surgery were double blindly randomized to treatment with recombinant human growth hormone (GH, n = 9) 24 IU or placebo (PL, n = 10) the first 5 postoperative days. All received parenteral nutrition (nitrogen = 5.7 +/- .1 g/m2, energy = 1018 +/- 12 kcal/m2 (125 +/- .7% of BMR) and epidural analgesia. Amino acid plasma levels and forearm fluxes were measured. RESULTS: The second postoperative day, growth hormone abolished forearm efflux of total amino acid nitrogen (GH: 170 +/- 117, PL: -785 +/- 192 nmol/100 mL/min, p = .0007) due to reduced losses of both essential and nonessential amino acids. Glutamine release was abolished (13 +/- 15 vs. -137 +/- 43 nmol/100 mL/min, p = .007) and alanine release attenuated (-61 +/- 17 vs. -211 +/- 51 nmol/100 mL/min, p = .01). 3-Methyl-histidine release was attenuated (-.20 +/- .11 vs. -.62 +/- .09 nmol/100 mL/min, p = .04). Growth hormone also induced decreased venous plasma amino acid levels. CONCLUSIONS: When given after gastrointestinal surgery in patients treated with total parenteral nutrition, growth hormone treatment abolished glutamine, 3-methylhistidine, and total amino acid nitrogen loss from forearm tissue. Alanine loss from forearm tissue was attenuated.     

Lazaroid U74500A as an additive to University of Wisconsin solution for pulmonary grafts in the rat transplant model.

Lazaroids are a class of novel 21 aminosteroids. They have been reported to be potent inhibitors of lipid peroxidation, which is a major contributing factor to ischemia-reperfusion injury in the lung. A Lewis rat orthotopic left lung isotransplant model was used to investigate the effects of the lazaroid U74500A on pulmonary preservation. The heart-lung blocks of donor rats were flushed with and then stored in either standard University of Wisconsin solution or University of Wisconsin solution with 30 mumol/L of U74500A substituted for the dexamethasone. After 6 or 12 hours of cold storage at 0 degrees C, the left lungs were transplanted into recipient rats and reperfused for 1 hour. Pulmonary function was assessed by measuring oxygen and carbon dioxide tensions in arterial blood after removal of the right lung. Lipid peroxide concentrations were measured as a thiobarbituric acid-reactive substance. Although arterial oxygen and carbon dioxide pressures and water content after 6 hours of preservation followed by reperfusion were similar in both the lazaroid and dexamethasone groups, lipid peroxide concentration was significantly higher in the dexamethasone group (0.88 +/- 0.07 mumol/gm) than in the lazaroid group (0.54 +/- 0.07 mumol/gm) (p < 0.01). After 12 hours of preservation, there were significant differences between the lazaroid and dexamethasone groups in arterial oxygen pressure (339 +/- 70 vs 27 +/- 3 mm Hg, p < 0.01), arterial carbon dioxide pressure (24.3 +/- 2.7 vs 47.7 +/- 7.0 mm Hg, p < 0.001), and lipid peroxide concentrations (0.69 +/- 0.07 vs 1.30 +/- 0.09 mumol/gm, p < 0.001). We conclude that addition of U74500A to the flush and storage solution enhances the preservation of the pulmonary graft in this transplant model.     

Postoperative alterations in interorgan glutamine exchange in enterectomized dogs

The effect of enterectomy on postoperative visceral organ glutamine exchange was studied in order to gain further understanding of the role of the intestinal tract in the altered glutamine metabolism that occurs following catabolic illness. In addition to studying glutamine, which transports 1/3 of whole blood amino acid nitrogen, we determined the fluxes of glutamate and alanine across the gastrointestinal tract, liver, and kidneys in 18 postoperative dogs. Arterial glutamine and glutamate were significantly higher in enterectomized animals than in controls. With enterectomy the gut became an organ of glutamine balance while in control dogs the GI tract consumed glutamine (0.11 +/- 0.04 vs 1.67 +/- 0.14 mumole/kg X min, P less than 0.001). The gut switched from an organ of glutamate release to one of net glutamate uptake following enterectomy and intestinal alanine release simultaneously fell by 50%. Simultaneously, the liver reduced its uptake of alanine and became an organ of glutamine release. Renal glutamine consumption was also diminished in enterectomy animals. The interorgan exchange of glutamine and other amino acids is altered by enterectomy. The increase in circulating glutamine levels in enterectomized animals suggests that the accelerated intestinal glutamine consumption that characterizes catabolic illnesses contributes to the low glutamine levels in these stress states. In addition, it becomes apparent that the gut is an important supplier of alanine to the liver, which supports gluconeogenesis. Metabolic adaptation and cooperation between organs is essential during organ absence or dysfunction if the organism is to survive critical illness.     

Influence of enterectomy on peripheral tissue glutamine efflux in critically ill patients

Glutamine and alanine are dominant nitrogen carriers from skeletal muscle stores to splanchnic organs. In addition, these amino acids may also serve as a primary energy source for the gastrointestinal tract during injury. To investigate these contributions, we studied extremity amino acid efflux during hypocaloric dextrose feedings and during total parenteral nutrition in a population of normal volunteers (NL VOL) (n = 9), a group of patients with sepsis who had undergone laparotomy without bowel resection and were in the intensive care unit (ICU) (n = 7), and patients with sepsis after laparotomy (PT) (n = 2) who had recently undergone greater than 80% bowel resection. Circulating alanine and glutamine levels were significantly lower in the patients compared with NL VOL under both feeding conditions. The peripheral output of alanine was higher in the ICU group than in the NL VOL during hypocaloric feedings. Glutamine efflux, however, was independent of either the counterregulatory hormone or substrate background. By contrast, enterectomy was associated with a marked decrease of extremity glutamine efflux compared with NL VOL or the ICU patients who did not undergo enterectomy (-62 +/- 9 nmol/min/dl tissue in the PT vs -265 +/- 32 nmol/min/dl tissue in the NL VOL and -311 +/- 58 nmol/min/dl tissue in the ICU group) during the dextrose feedings; this difference persisted during subsequent total parenteral nutrition (+12 +/- 13 nmol/min/dl tissue in PT vs -178 +/- 56 nmol/min/dl tissue in the NL VOL and -287 +/- 81 nmol/min/dl tissue in the ICU group). These data suggest that distinct mechanisms regulate peripheral alanine and glutamine balance and that the gastrointestinal tract provides a feedback signal to peripheral tissues to maintain glutamine mobilization under both nonstressed and stressed conditions.     

Effect of in vivo contact between blood and dialysis membranes on protein catabolism in humans

To investigate whether the contact between blood and dialysis membranes might induce muscle protein degradation, the exchange of free amino acids across leg tissues was measured by catheterization technique in three groups of healthy subjects before and after a 150 minute sham-hemodialysis procedure (SHDP), that is, in vivo passage of blood (100 ml/min) through a dialyzer but with no circulating dialysate. Dialyzers with either regenerated cellulose membrane (group CU, N = 10 and group CU-IND, N = 6) or polyacrylonitrile membrane (group AN, N = 8) were used in group CU-IND indomethacin was administered before (100 mg) and at the end (50 mg) of SHDP. Leg blood flow was measured by venous occlusion plethysmography. In group CU net leg release of tyrosine and phenylalanine increased from 3.4 +/- 0.8 and 3.6 +/- 0.8 nmol/min/100 g tissue, respectively, before SHDP to 7.8 +/- 1.8 and 8.3 +/- 1.8 nmol/min/100 g tissue, respectively, at 345 minutes after the start of SHDP (P less than 0.01). The total release of all measured amino acids increased from 148 +/- 31 to 309 +/- 50 nmol/min/100 g tissue (P less than 0.01). The results indicate that interaction between blood and regenerated cellulose membranes leads to accelerated net protein breakdown. In group CU-IND no change in leg amino acid release was observed following SHDP, suggesting that the increased net protein catabolism is mediated by prostaglandins. Sham hemodialysis using AN membranes did not result in increased amino acid efflux from leg tissues, implying that the protein catabolic effect of blood-membrane contact depends on the biochemical properties of dialyser.     

Brush border transport of glutamine and other substrates during sepsis and endotoxemia

The effects of severe infection on luminal transport of amino acids and glucose by the small intestine were investigated. Studies were done in endotoxin-treated rats and in septic patients who underwent resection of otherwise normal small bowel. In rats the kinetics of the brush border glutamine transporter and the glutaminase enzyme were examined. In patients the effects of severe infection on the transport of glutamine, alanine, leucine, and glucose were studied. Transport was measured using small intestinal brush border membrane vesicles that were prepared by Mg++ aggregation/differential centrifugation. Uptake of radiolabeled substrate was measured using a rapid mixing/filtration technique. Vesicles demonstrated 15-fold enrichments of enzyme markers, classic overshoots, transport into an osmotically active space, and similar 2-hour equilibrium values. The sodium-dependent pathway accounted for nearly 90% of total carrier-mediated transport. Kinetic studies on rat jejunal glutaminase indicated a decrease in activity as early as 2 hours after endotoxin secondary to a decrease in enzyme affinity for glutamine (Km = 2.23 +/- 0.20 mmol/L [millimolar] in controls versus 4.55 +/- 0.67 in endotoxin, p less than 0.03), rather than a change in Vmax. By 12 hours the decrease in glutaminase activity was due to a decrease in Vmax (222 +/- 36 nmol/mg protein/min in controls versus 96 +/- 16 in endotoxin, p less than 0.03) rather than a significant change in Km. Transport data indicated a decrease in sodium-dependent jejunal glutamine uptake 12 hours after endotoxin secondary to a 35% reduction in maximal transport velocity (Vmax = 325 +/- 12 pmol/mg protein/10 sec in controls versus 214 +/- 8 in endotoxin, p less than 0.0001) with no change in Km (carrier affinity). Sodium-dependent glutamine transport was also decreased in septic patients, both in the jejunum (Vmax for control jejunum = 786 +/- 96 pmol/mg protein/10 sec versus 417 +/- 43 for septic jejunum, p less than 0.01) and in the ileum (Vmax of control ileum = 1126 +/- 66 pmol/mg protein/10 sec versus 415 +/- 24 in septic ileum, p less than 0.001) The rate of jejunal transport of alanine, leucine, and glucose was also decreased in septic patients by 30% to 50% (p less than 0.01). These data suggest that there is a generalized down-regulation of sodium-dependent carrier-mediated substrate transport across the brush border during severe infection, which probably occurs secondary to a decrease in transporter synthesis or an increase in the rate of carrier degradation.(ABSTRACT TRUNCATED AT 400 WORDS)     

In a canine model, lung preservation at 10 degrees C is superior to that at 4 degrees C. A comparison of two preservation temperatures on lung function and on adenosine triphosphate level measured by phosphorus 31-nuclear magnetic resonance.

Techniques for organ preservation generally use hypothermia to retard metabolic requirements. However, excessive hypothermia may also produce injury. Using a canine left lung allotransplantation procedure, we compared two preservation temperatures (4 degrees and 10 degrees C) in terms of subsequent lung function measured by temporary occlusion of the right pulmonary artery after implantation of the preserved left donor lung. The lungs were flushed with low-potassium dextran electrolyte solution, inflated with 100% oxygen, and preserved for 18 hours. To investigate possible changes of energy stores at different temperatures, we performed phosphorus 31-nuclear magnetic resonance analyses of lung samples. Sequential determinations of adenosine triphosphate levels in lung tissue preserved at 4 degrees, 10 degrees, and 22 degrees C were studied. After transplantation, lungs preserved at 10 degrees C (n = 6) provided significantly better arterial oxygen tension than those preserved at 4 degrees C (n = 6), 451 +/- 46 mm Hg versus 243 +/- 86 mm Hg (p less than 0.05), and lower pulmonary vascular resistance, 581 +/- 68 dynes.sec.cm-5 versus 1006 +/- 157 dynes.sec.cm-5 (p less than 0.05). Adenosine triphosphate levels at 4 degrees and 10 degrees C were stable and did not differ from each other at the end of the 18-hour preservation period: 0.86 +/- 0.04 mumol/gm wet weight for control versus 0.86 +/- 0.07 mumol/gm wet weight for 4 degrees C and 0.93 +/- 0.06 mumol/gm wet weight for 10 degrees C after 18 hours of preservation. Preservation at 22 degrees C caused a 28% depression of adenosine triphosphate after 18 hours of preservation. These results lead us to conclude the following: (1) Optimal temperature for lung preservation is in the vicinity of 10 degrees C, and (2) lung dysfunction caused by excessive hypothermia is not due to a failure to maintain adenosine triphosphate levels. We suspect that adenosine triphosphate is generated by oxidative phosphorylation during lung preservation.     

Aerodynamic evaluation of crystalloid and colloid flush perfusion for lung preservation

To assess the effectiveness of pulmonary perfusion we evaluated the lung mechanics of 36 canine lungs in an isolated perfused working lung (IPWL) model. Four groups of lungs (n = 9 each) were preserved by pulmonary artery flushing with either high-potassium colloid (UW), high-potassium crystalloid (EuroCollins', EC), low-potassium crystalloid control (lactate), or low-potassium substrate-enhanced crystalloid (RPMI) followed by 130 +/- 10 min of cold storage. Ventilation remained constant (TV 10 ml/kg at 14 breaths/min with 5 cm H2O PEEP). Assessed data included lung resistance (R), timed expiratory volume (EV0.3 sec as %TV), lung compliance (C), elastic work (Wel), and flow-resistive work (Wres). Immediately following storage, R and Wel were similar for all groups (16 +/- 3 cm H2O/liter/sec and 149 +/- 18 gm/min). UW preserved lungs were less compliant (1.5 +/- 0.1 X 10(-2) liter/cm H2O) and required more inspiratory work (Wres 5.8 +/- 0.8 gm/min) compared to the low-potassium crystalloid (Lactate) group (2.0 +/- 0.1 X 10(-2) liter/cm H2O and 3.4 +/- 0.6 gm/min, respectively, P less than 0.05). For 3 hr of reperfusion, crystalloid lungs showed no significant change in R, C, Wel, or Wres. In contrast, R of the UW group increased significantly to 32 +/- 5 and 40 +/- 8 cmH2O/liter/sec at 1 and 3 hr, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)     

Glucose uptake and amino acid metabolism in perfused hearts from tumor-bearing rats

The purpose of this study was to evaluate whether heart glucose metabolism can account for elevated heart oxygen consumption in a tumor-bearing host. This is the first report of altered metabolism in perfused hearts from tumor-bearing animals. Glucose, glycerol, lactate, and amino acid metabolism was examined under steady-state conditions in isolated perfused hearts from sarcoma-bearing rats and compared to the metabolism in hearts from starved (96 hr) and fed control rats. Heart dry weight was reduced by 10% in tumor-bearing rats and by 30% in starved rats when compared to freely fed control animals. Cardiac glucose uptake was decreased in tumor-bearing rats (206 +/- 33 mumoles/hr/g dry wt) compared to both starved (298 +/- 18) and fed control rats (293 +/- 25). Hearts from both fed and starved controls released lactate and glycerol at significant rates during perfusion which was not evident in hearts from tumor-bearing rats. The release of individual amino acids from working hearts during perfusion was different among the animal groups with a severe depression of both glutamine and alanine release in tumor-bearing rats. In starved rats alanine release was normal although glutamine release was depressed by more than 50%. The net release of all amino acids was lowest in hearts from tumor-bearing rats, intermediate in the starved animals, and highest in the control animals, while the nonmetabolized amino acids (phenylalanine, tyrosine, methionine) were released at increased rates only from tumor-host hearts, indicating an increased net breakdown of some cardiac proteins in tumor-bearing animals.(ABSTRACT TRUNCATED AT 250 WORDS)     

Impaired response of the denervated kidney to endothelin receptor blockade in normotensive and spontaneously hypertensive rats

BACKGROUND: As yet, there are only limited data available on the exact role of endothelin (ET) acting through endothelin-A (ETA) receptors in renal sodium and water regulation and the potential functional implications of an interaction of the renal ET system with renal nerves in normotensive and spontaneously hypertensive rats. METHODS: Experiments were carried out in 64 male conscious spontaneously hypertensive rats and in 56 normotensive Wistar-Kyoto (WKY) rats. Bilateral renal denervation (BRD) was performed in 32 spontaneously hypertensive rats and 28 WKY rats 7 days before the experiments. The ETA receptor antagonist, BQ-123 (16.4 nmol/kg x min intravenously) or the endothelin-B (ETB) receptor antagonist, BQ-788 (25 nmol/kg x min intravenously) were infused at a rate of 25 microL/min for 50 minutes. RESULTS: Renal papillary ET-1 concentration in intact spontaneously hypertensive rats was 67.8% lower than in intact WKY rats (154 +/- 40 fmol/mg protein vs. 478 +/- 62 fmol/mg protein, P < 0.01). BRD decreased papillary ET-1 by 73.5% in WKY rats to 127 +/- 19 fmol/mg protein (P < 0.001), but had no effect in spontaneously hypertensive rats (122 +/- 37 fmol/mg protein). BRD, BQ-123, or BQ-788 did not affect glomerular filtration rate (GFR) or renal blood flow (RBF) in any of the groups. In intact WKY, BQ-123 decreased urine flow rate (V) from 4.65 +/- 0.44 microL/min.100 g body weight to 2.44 +/- 0.35 microL/min.100 g body weight (P < 0.01), urinary excretion of sodium (UNaV) from 238.2 +/- 27.4 to 100.2 +/- 17.0 (P < 0.01) and potassium (UKV) from 532.1 +/- 62.6 nmol/min.100 g body weight to 243.0 +/- 34.2 nmol/min.100 g body weight (P < 0.001), whereas BQ-788 decreased only V and UNaV. In renal denervated WKY, BQ-123 or BQ-788 did not alter V, UNaV, or UKV. In intact spontaneously hypertensive rats BQ-123 but not BQ-788 decreased V from 3.94 +/- 0.48 microL/min.100 g body weight to 2.55 +/- 0.44 microL/min.100 g body weight (P < 0.05). In renal denervated spontaneously hypertensive rats neither BQ-123 nor BQ-788 affected V, UNaV, or UKV. CONCLUSION: An interaction between ET and renal nerves is involved in the control of renal function. Moreover, renal nerves participate in the regulation of ET-1 production within the kidney. Finally, decreased synthesis of ET-1 in the renal papilla of spontaneously hypertensive rats may contribute to development and/or maintenance of hypertension due to modulation of renal excretory function.     

Decreased rat hepatic guanylate cyclase activity in streptozotocin-induced diabetes mellitus.

Guanylate cyclase is found in virtually all cells, but its physiologic role and the effect of hormones on its activity have not been clarified. Hepatic soluble guanylate cyclase activity (37,000 g supernatant) in rats with diabetes-mellitus-like syndrome induced by streptozotocin, 65 mg./kg. i.v., was 140 +/- 8 pmoles accumulated/mg. protein/10 min. (n = 13 rats) as against 279 +/- 16 pmoles accumulated/mg. protein/10 min. (n = 12 rats) in normal rats. The average blood sugar for the 12 normal rats was 100 +/- 4 mg./100 ml. and 546 +/- 32 mg./100 ml. for 13 diabetic rats. The decreased soluble hepatic guanylate cyclase activity in diabetic rats was completely restored to normal with 10 U. regular insulin, i.p. The maximum increase in guanylate cyclase activity was observed as early as five minutes and as late as two hours after insulin administration. Insulin restoration of guanylate cyclase was dose-related over a range of 1 U. to 10 U., i.p. Hepatic cyclic GMP levels in vivo paralleled in-vitro guanylate cyclase activity, being 29 +/- 0.4 pmoles/gm. wet weight in normals, 17 +/- 0.4 pmoles/gm. wet weight in streptozotocin-diabetic rats, and 38 +/- 0.4 pmoles/gm. wet weight two hours after the injection of 10 U. regular insulin. We conclude that rat hepatic guanylate cyclase is decreased in streptozotocin-induced diabetes and that insulin modulates this enzyme. The administration of exogenous insulin in normal animals did not further augment hepatic guanylate cyclase activity.     

Adaptive regulation of alanine transport in hepatic plasma membrane vesicles from the endotoxin-treated rat

The mechanisms by which hepatic alanine consumption is increased during endotoxemia were investigated to gain further insight into the altered amino acid metabolism which characterizes critical illness. Rats were studied 12 hr after receiving endotoxin (ENDO) or saline. Hepatic alanine delivery was determined in vivo and hepatic alanine content was measured. Hepatocyte transport activity was studied by evaluation of [3H]-alanine accumulation in hepatocyte plasma membrane vesicles (HPMVs). Vesicle integrity was demonstrated by electron microscopy and a 14-fold enrichment in 5'-nucleotidase. Endotoxin treatment resulted in a state of hyperalaninemia and a threefold increase in hepatic alanine delivery (2.79 +/- 0.17 mu mole/100 g body weight/min in controls vs 8.13 +/- 0.98 in ENDO animals; P less than 0.001). Data from HPMVs revealed the presence of a high- and low-affinity component of alanine transport. Endotoxin treatment resulted in a 30% decrease in the Vmax of the high-affinity transport component (3355 +/- 177 pmole/mg protein/10 sec in controls vs 2338 +/- 270 in the ENDO group; P less than 0.05). Concomitant with the observed changes in alanine delivery and transport activity, endotoxin treatment resulted in a 56% rise in hepatic alanine content (2.53 +/- 0.29 mu mole/g liver in controls vs 3.95 +/- 0.23 in ENDO; P less than 0.005). These data indicate that the accelerated hepatic alanine consumption which occurs during endotoxemia is primarily the result of increased hepatic substrate delivery. Despite the resultant repression of transport activity, delivery begins to outdistance the metabolic capacity of the hepatocyte to utilize alanine and intracellular alanine levels rise.     

The effects of sepsis and endotoxemia on gut glutamine metabolism.

The effects of sepsis on gut glutamine (GLN) metabolism were studied to gain further insight into the regulation of the altered glutamine metabolism that characterizes critical illnesses. Studies were done in laboratory rats and in hospitalized patients. The human studies were done in seven healthy surgical patients (controls) and six septic patients who underwent laparotomy. Radial artery and portal vein samples were obtained during operation and were analyzed for GLN and oxygen content. Despite no reduction in arterial glutamine concentration in the septic patients, gut glutamine extraction was diminished by 75% (12.0% +/- 1.6% in controls vs. 2.8% +/- 0.8% in septic patients, p less than 0.01). Similarly gut oxygen extraction was diminished by nearly 50% in the septic patients (p less than 0.05). To further investigate these abnormalities, endotoxin (10 mg/kg intraperitoneally) or saline (controls) was administered to adult rats 12 hours before cannulation of the carotid artery and portal vein. The arterial GLN concentration was increased by 13% in the endotoxin-treated animals (p less than 0.05) but gut glutamine uptake was diminished by 46% (526 +/- 82 nmol/100 g BW/minute in controls vs. 282 +/- 45 in endotoxin, p less than 0.01). Simultaneously gut glutaminase activity was diminished by 30% (p less than 0.01) and intestinal glutamate release fell by two thirds. Blood cultures were negative in control animals (0 of 20), but were positive in 25% of endotoxemic animals (6 of 24) for gram-negative rods (p = 0.019). Sepsis and endotoxemia impair gut glutamine metabolism. This impairment may be etiologic in the breakdown of the gut mucosal barrier and in the development of bacterial translocation.