Effects of ozone on lung mechanics and cyclooxygenase metabolites in dogs.

To determine if acute exposure to ozone can cause changes in the production of cyclooxygenase metabolites of arachidonic acid (AA) in the lung which are associated with changes in lung mechanics, we exposed mongrel dogs to 0.5 ppm ozone for two hours. We measured pulmonary resistance (RL) and dynamic compliance (Cdyn) and obtained methacholine dose response curves and bronchoalveolar lavagate (BAL) before and after the exposures. We calculated the provocative dose of methacholine necessary to increase RL 50% (PD50) and analyzed the BAL for four cyclooxygenase metabolites of AA: a stable hydrolysis product of prostacyclin, 6-keto-prostaglandin F1 alpha (6-keto-PgF1 alpha); prostaglandin E2 (PgE2); a stable hydrolysis product of thromboxane A2, thromboxane B2 (TxB2); and prostaglandin F2 alpha (PgF2 alpha). Following ozone exposure, RL increased from 4.75 +/- 1.06 to 6.08 +/- 1.3 cm H2O/L/sec (SEM) (p less than 0.05), Cdyn decreased from 0.0348 +/- 0.0109 TO .0217 +/- .0101 L/cm H2O (p less than 0.05), and PD50 decreased from 4.32 +/- 2.41 to 0.81 +/- 0.49 mg/cc (p less than 0.05). The baseline metabolite levels were as follows: 6-keto PgF1 alpha: 96.1 +/- 28.8 pg/ml; PgE2: 395.8 +/- 67.1 pg/ml; TxB2: 48.5 +/- 11.1 pg/ml; PgF2 alpha: 101.5 +/- 22.6 pg/ml. Ozone had no effect on any of these prostanoids. These studies quantify the magnitude of cyclooxygenase products of AA metabolism in BAL from dog lungs and demonstrate that changes in their levels are not prerequisites for ozone-induced changes in lung mechanics or airway reactivity.     

Lung mechanics and airway reactivity in sheep during development of oxygen toxicity

The causes of respiratory distress in O2 toxicity are not well understood. The purpose of this study was to better define the airway abnormalities caused by breathing 100% O2. Sheep were instrumented for measurements of dynamic compliance (Cdyn), functional residual capacity by body plethysmography (FRC), hemodynamics, and lung lymph flow. Each day Cdyn and FRC were measured before, during, and after the application of 45 min continuous positive airway pressure (CPAP) at 15 cmH2O. The amount of aerosol histamine necessary to reduce Cdyn 35% from baseline (ED35) was measured each day as was the response to aerosol metaproterenol. Cdyn decreased progressively from 0.083 +/- 0.005 (SE) 1/cmH2O at baseline to 0.032 +/- 0.004 l/cm H2O at 96 h of O2. Surprisingly, FRC did not decrease (1,397 +/- 153 ml at baseline vs. 1,523 +/- 139 ml at 96 h). The ED35 to histamine did not vary among days or from air controls. Metaproterenol produced a variable inconsistent increase in Cdyn. We also measured changes in Cdyn during changes in respiratory rate and static pressure-volume relationships in five other sheep. We found a small but significant frequency dependence of compliance and an increase in lung stiffness with O2 toxicity. We conclude that in adult sheep O2 toxicity reduces Cdyn but does not increase airway reactivity. The large reduction in Cdyn in O2 toxicity results from processes other than increased airway reactivity or reduced lung volume, and Cdyn decreases before the development of lung edema.     

Endotoxemia causes increased lung tissue lipid peroxidation in unanesthetized sheep

Our purpose was to determine whether lipid peroxidation of lung tissue, a reflection of O2 radical injury, occurs with endotoxin, and whether the degree of tissue change corresponds with the degree of increased protein permeability. Unanesthetized adult sheep with lung lymph fistulas were given Escherichia coli endotoxin at a dose of 2 micrograms/kg (n = 34). Tissue lipid peroxidation was measured using the thiobarbituric acid assay for malondialdehyde (MDA). The MDA content of lung tissue in nanomoles per gram increased from a control value of 48 +/- 8 to 98 +/- 18 at 5 h postendotoxin (2 micrograms/kg), whereas lung lymph protein transport (Cp), was increased 3- to 4-fold. The MDA content returned to base line with Cp by 24 h postendotoxin. Six sheep given endotoxin were pretreated with 12.5 mg/kg of ibuprofen, and six were infused with dimethylthiourea (DMTU) 0.75 g/kg. With ibuprofen, Cp was only increased 2.5- to 3-fold and MDA was increased to 69 +/- 15 nmol/g. With DMTU, the increase in Cp was comparable to that with endotoxin alone, as was the MDA of lung tissue with a value of 92 +/- 12 nmol/g. The correlation of tissue MDA with Cp in all animals was 0.83. We conclude that lipid peroxidation occurs in lung tissue after a moderately severe endotoxin injury with the degree of change corresponding to the degree of increased Cp.     

Pulmonary intravascular macrophages and hemodynamic effects of liposomes in sheep

We studied the effects of liposomes on the pulmonary circulation of sheep and found a close correlation between liposome retention in the lung and the intravascular macrophages. A test dose of liposomes (5.5 mumol of total lipids) injected intravenously transiently increased pulmonary arterial pressure from 24 +/- 2 to 55 +/- 16 (SD) cmH2O. The pulmonary arterial pressure responses were dose dependent and reproducible. The rise in pulmonary arterial pressure was blocked completely by indomethacin and 75% by a thromboxane synthase inhibitor. Systemic arterial thromboxane B2 concentration increased from a base-line level of less than 50 pg/ml to 250 +/- 130 pg/ml at the peak of the pressor response. Larger doses of liposomes (220 mumol of total lipids) infused intravenously over 1 h increased pulmonary arterial pressure maximally within the first 15 min. Lymph flow increased and lymph protein concentration decreased, suggesting venoconstriction. Over half (62.4 +/- 15.7%) of 111In-labeled liposomes remained in the lung after 2 h. Fluorescence and transmission electron microscopy showed that greater than 90% of the liposomes were associated with mononuclear cells in the lumen of the alveolar wall microvessels. We conclude that liposomes affect pulmonary arterial pressure transiently by a mechanism involving the arachidonate cascade, principally thromboxane. Our observations suggest that a population of pulmonary intravascular macrophages is likely to be the source of the thromboxane and the pulmonary hemodynamic and lymph dynamic changes that occur in a dose-dependent fashion, although interactions between liposomes, leukocytes, or endothelial cells, in addition to the macrophages, have not been completely ruled out. We believe this is the first demonstration that pulmonary intravascular macrophages may be the source of the arachidonate metabolites rather than endothelial cells, neutrophils, or perivascular interstitial cells.     

Hyperbaric oxygen toxicity: role of thromboxane.

Exposing rabbits for 1 h to 100% O2 at 4 atm barometric pressure markedly increases the concentration of thromboxane B2 in alveolar lavage fluid [1,809 +/- 92 vs. 99 +/- 24 (SE) pg/ml, P less than 0.001], pulmonary arterial pressure (110 +/- 17 vs. 10 +/- 1 mmHg, P less than 0.001), lung weight gain (14.6 +/- 3.7 vs. 0.6 +/- 0.4 g/20 min, P less than 0.01), and transfer rates for aerosolized 99mTc-labeled diethylenetriamine pentaacetate (500 mol wt; 40 +/- 14 vs. 3 +/- 1 x 10(-3)/min, P less than 0.01) and fluorescein isothiocyanate-labeled dextran (7,000 mol wt; 10 +/- 3 vs. 1 +/- 1 x 10(-4)/min, P less than 0.01). Pretreatment with the antioxidant butylated hydroxyanisole (BHA) entirely prevents the pulmonary hypertension and lung injury. In addition, BHA blocks the increase in alveolar thromboxane B2 caused by hyperbaric O2 (10 and 45 pg/ml lavage fluid, n = 2). Combined therapy with polyethylene glycol- (PEG) conjugated superoxide dismutase (SOD) and PEG-catalase also completely eliminates the pulmonary hypertension, pulmonary edema, and increase in transfer rate for the aerosolized compounds. In contrast, combined treatment with unconjugated SOD and catalase does not reduce the pulmonary damage. Because of the striking increase in pulmonary arterial pressure to greater than 100 mmHg, we tested the hypothesis that thromboxane causes the hypertension and thus contributes to the lung injury. Indomethacin and UK 37,248-01 (4-[2-(1H-imidazol-1-yl)-ethoxy]benzoic acid hydrochloride, an inhibitor of thromboxane synthase, completely eliminate the pulmonary hypertension and edema.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of cyclooxygenase blockade on gas exchange and hemodynamics in Pseudomonas pneumonia

Acute bilateral Pseudomonas aeruginosa pneumonia was induced in 10 anesthetized dogs, after which five dogs received intravenous indomethacin (2 mg/kg) (indomethacin group), whereas five others were infused with saline (2 ml/kg) (control group). Plasma levels of 6-ketoprostaglandin F1 alpha(6-keto-PGF1 alpha) and thromboxane B2 (TxB2), stable metabolites of prostacyclin (PGI2) and thromboxane A2 (TxA2), respectively, were measured by radioimmunoassay. Although TxB2 levels were not different before and after inoculation in either group, 6-keto-PGF1 alpha levels increased from their base-line value in each animal as pneumonia developed (indomethacin group: less than 100 to 330 +/- 90 pg/ml; control group: less than 100 to 630 +/- 300 pg/ml). Both prostaglandins fell to less than 100 pg/ml in each dog after indomethacin infusion, whereas they remained elevated in the control group after infusion of normal saline. Perfusion of consolidated lung regions (Qp/QT), measured with radioactive microspheres and expressed as a percent of total pulmonary blood flow, was dramatically reduced after indomethacin (35 +/- 3 to 16 +/- 1%) with consequent improvement in pulmonary shunt (Qs/QT: 30 +/- 8 to 18 +/- 6%) and arterial O2 tension (PaO2: 123 +/- 25 to 274 +/- 77 Torr). These parameters remained unchanged or deteriorated further in the control group after infusion of saline. Three additional dogs with Pseudomonas pneumonia were studied in which the indomethacin-induced reduction in Qp/QT was substantially but not completely reversed by intravenous infusion of PGI2.(ABSTRACT TRUNCATED AT 250 WORDS)     

Thermal recovery after passage of the pulmonary circulation assessed by deconvolution

We determined the effect of H2O2 on both the physiological and biochemical lung changes seen in the adult sheep after endotoxin. Fourteen unanesthetized adult sheep with chronic lung lymph fistula were given Escherichia coli endotoxin (1 microgram/kg) over 30 min. Seven sheep were given catalase (32,500 U/kg body wt) as an intravenous bolus 30 min before endotoxin. Four sheep were given catalase alone. Oxidant lung changes were measured using arterial plasma conjugated dienes and lung tissue malondialdehyde (MDA) content, both reflecting the lipid peroxidation process. Animals were killed 5 h after endotoxin. We found that endotoxin alone caused an early increase in pulmonary arterial pressure lung lymph flow (QL), plasma thromboxane B2, 6-keto-prostaglandin F1 alpha, and plasma conjugated dienes. A decrease in cardiac output and arterial PO2 was also seen. A three- to four-fold increase in protein-rich QL was noted at 3-4 h as well as a continued increase in arterial conjugated dienes. Lung MDA and water content were also significantly increased from base line. Catalase pretreatment significantly attenuated both the physiological changes and the prostanoid and conjugated diene release. Lung MDA and water content also remained at base line. We conclude that H2O2 plays a major role in endotoxin-induced lung injury as well as the resulting lipid peroxidation process.     

Serum levels of TNF-alpha,sIL-2R,IL-6, and IL-8 are increased and associated with elevated lipid peroxidation in patients with Behçet's disease

AIM: Behçet''s disease (BD) is asystemic immunoinflammatory disorder and the aetiopathogenesis is to be specified. Cytokines play a role in immune response and in many inflammatory diseases. The aim of this case-control study is to investigate serum pro-inflammatory cytokine tumour necrosis factor (TNF)-alpha, interleukin-1beta (IL-1beta), soluble IL-2 receptor (sIL-2R), IL-6, and chemokine IL-8 levels in patients with BD. We also determined the end product of lipid peroxidation (malondialdehyde (MDA)) in BD patients as an index for oxidative stress. METHODS: A total of 37 patients (19 men, 18 women) with BD (active, n = 17; inactive, n = 20) and 20 age-matched and sex-matched healthy control subjects (11 men, nine women) included in this cross-sectional, blinded study. Serum TNF-alpha, IL-1beta, sIL-2R, IL-6 and IL-8 levels were determined by a spectrophotometer technique using the immulite chemiluminescent immunometric assay. Lipid peroxidation was evaluated by Wasowicz et aL The levels of cytokines and lipid peroxidation in the active period were compared with the inactive period of the disease. Results are expressed as mean +/- standard error. RESULTS: IL-1beta levels were below the detection limits of the assay (< 5 pg/ml) in all samples. Mean levels of MDA (8.1+/-0.7 micromol/l), sIL-2R (800+/-38 U/ml), IL-6 (12.6+/-1.1 pg/ml), IL-8 (7.2+/-0.4 pg/ml), and TNF-alpha (7.9+/-0.5 pg/ml) in active BD patients were significantly higher than those in inactive patients (4.3+/-0.5 micromol/l, p < 0.01; 447+/-16 U/ml, p < 0.001; 8.3+/-0.6 pg/ml, p = 0.006; 5.3+/-0.1 pg/ml, p < 0.001; and 5.1 0.2 pg/ml, p < 0.001; respectively) or control subjects (2.1+/-0.2 micromol/l, p < 0.001; 446+/-20 U/ml, p < 0.001; 6.4+/-0.2 pg/ml, p < 0.001; 5.4+/-0.1 pg/ml, p < 0.001; and 4.7+/-0.1 pg/ml, p < 0.001, respectively). On the contrary, only the mean IL-6 level was significantly different between inactive BD and control subjects (p = 0.02). All acute phase reactants were significantly higher in active BD than in inactive period (for each, p < 0.01). Conclusions: High levels of sIL-2R, IL-6, IL-8 and TNF-alpha indicate the activation of immune system in BD. Serum sIL-2R, IL-6, IL-8 and TNF-alpha seem to be related to disease activity. Increased lipid peroxidation suggests oxidative stress in BD and therefore tissue damage in such patients. Amelioration of clinical manifestations would be envisaged by targeting these cytokines, chemokines and lipid peroxidation with pharmacological agents.     

Role of contaminating platelets in thromboxane synthesis in primary cultures of human umbilical vein endothelial cells

Previous studies suggested that cultured human endothelial cells metabolize arachidonic acid to thromboxane A2. When primary cultures of human umbilical vein endothelial cells were incubated with 14C-arachidonic acid and the 14C-metabolites resolved by reverse phase high pressure liquid chromatography, radioactive products were observed that comigrated with 6-keto-prostaglandin F1alpha and thromboxane B2, the degradation products of prostacyclin and thromboxane A2, respectively. Since platelets synthesize thromboxane A2, the present study examined the hypothesis that adherent platelets may contaminate the primary cultures of human umbilical vein endothelial cells and be responsible for thromboxane B2 production. Confluent primary cultures or passaged cells were stimulated with histamine (10(-5) M). Incubation buffer was analyzed by specific radioimmunoassays for 6-keto-prostaglandin F1alpha and thromboxane B2. The production of thromboxane B2 decreased in the passaged cells (207 +/- 44 pg/ml versus 65 +/- 12 pg/ml; primary versus passaged cells). A moderate decrease in the yield of 6-keto-prostaglandin F1alpha was measured in the passaged cells compared to the primary cultures (3159 +/- 356 pg/ml versus 1678 +/- 224 pg/ml, primary versus passaged cells). If the primary cultures were incubated with human platelet-rich plasma for 30 min prior to stimulation with histamine, the amount of thromboxane B2 increased approximately 10-fold. In an additional experiment, sub-confluent primary cells were incubated with platelet-rich plasma for 30 min, washed to remove non-adherent platelets, and allowed to reach confluency. Confluent cells were then passaged and stimulated with histamine. The amount of thromboxane B2 was not significantly different from that obtained with passaged cells that had not been incubated with platelet-rich plasma during the primary culture (83 +/- 15 pg/ml versus 65 +/- 12 pg/ml, respectively). If the cyclooxygenase inhibitor indomethacin was included in the incubations, the amounts of both thromboxane B2 and 6-keto-prostaglandin F1alpha decreased. In contrast, the thromboxane A2 synthase inhibitor dazoxiben blocked thromboxane production and had no effect on the amount of 6-keto-prostaglandin F1alpha. Light microscopy revealed the presence of adherent platelets in primary cultures with and without platelet-rich plasma but no platelets were observed in any group of passaged cells. Histofluorescence for platelet serotonin indicated the presence of platelets only in primary cultures of human umbilical vein endothelial cells or in cultures pre-incubated with platelet-rich plasma. These studies suggest that primary cultures of human umbilical vein endothelial cells contain adherent platelets that contribute to thromboxane synthesis.     

Endotoxemia produces an increase in arterial but not venous lipid peroxides in sheep

Our purpose was to determine the effect of an endotoxin-induced lung injury on circulating lipid peroxides. We measured both malondialdehyde (MDA) and conjugated dienes (as optical density at 233 nm) in aortic and venous plasma and lung lymph in 10 unanesthetized sheep given 1 microgram/kg of Escherichia coli endotoxin. Total lipids and prostanoids 6-ketoprostaglandin F1 alpha and thromboxane B2 were also measured. Six control sheep were also studied. Animals were monitored for a 12-h period and then killed, and lung tissue MDA was determined. A two-phase endotoxin response was noted with an initial pulmonary hypertension followed by a steady-state increase in protein-rich lung lymph flow (QL) between a 3- and 6-h period. Aortic plasma MDA was significantly increased from a base line of 4.8 +/- 1.4 to 8.9 +/- 1.6 and 7.5 +/- 1.3 nmol/ml at 1 and 4 h post-endotoxin. Aortic plasma conjugated dienes increased in all 10 sheep post-endotoxin. Venous levels of both MDA and conjugated dienes were not significantly increased. Lung QL increased two- to three-fold. Lung lymph MDA increased significantly at 1 h post-endotoxin. Lymph conjugated dienes decreased. Plasma and lymph lipid peroxide levels returned to base line by 12 h in most animals. However, tissue MDA remained significantly increased in all sheep from base line of 45 +/- 9 to 85 +/- 14 nmol/g tissue. We conclude that both MDA and conjugated dienes are transiently released into aortic plasma during endotoxin-induced oxidant lung injury.(ABSTRACT TRUNCATED AT 250 WORDS)     

Synthesis of prostaglandins, TXA2 and PGI2, during one lung anesthesia

This study is to determine histamine, serotonin, TXA2 and PGI2 to be the cause of Hypoxic Pulmonary Vasoconstriction (HPV) at the same time of one lung ventilation and thoracotomy. Five patients who were to undergo upper-lobe resection of the right lung, were included in this study. All patients underwent same premedication and anesthetic method. Endotracheal intubation was done with a Univent tracheal tube. Gas analysis and determinations of the substances were done at six times in total. Respiratory Index (RI) began to increase immediately after the start of one lung ventilation. Post-thoracotomy RI further increased. After closing of the thorax, RI returned to the control values. Serotonin and histamine showed no change in any case throughout the experiment. TXB2 began to increase along with the start of one lung ventilation. The 15-min value was 167.2 +/- 85.8 pg/ml and 30-min value was 345.6 +/- 261.2 pg/ml, showing significant increase. The values of 6-keto PGF1 alpha were 22.6 +/- 2.9 pg/ml (15-min value), 89.6 +/- 52.3 pg/ml (30-min value), 290.8 +/- 120.1 pg/ml (post opening value) and 84.4 +/- 21.3 pg/ml (post-closing value). In our study, we concluded that neither serotonin nor histamine was the direct factor of HPV. TXA2 was the direct chemical mediator of HPV and PGI2 showed a negative feedback to the pulmonary vasoconstriction.     

Pharmacological modulation of prostacyclin and thromboxane production of rat and cat venous tissue slices.

To reveal a potential modulating effect of vasoactive pharmacological agents on the prostanoid production of the venous wall, prostacyclin and thromboxane release from venous tissue slices was studied. Aortic and caval vein samples from 20 rats as well as from 21 cats were studied. Prostacyclin and thromboxane productions were determined by radioimmunoassay as 6-keto-PGF1 alpha and TxB2 released into the incubation medium. Venous tissue produced significantly less prostacyclin per unit weight than arterial tissue in rats (30.7 +/- 4.6 vs. 52.1 +/- 8.2 pg/mg/min), while in cats an opposite situation was found (16.6 +/- 3.2 vs. 7.06 +/- 1.9 pg/mg/min). Thromboxane production of venous tissue was consequently higher than corresponding values for aortic tissue (3.72 +/- 0.46 vs. 1.54 +/- 0.14 in rats and 3.4 +/- 0.6 vs. 1.33 +/- 0.19 in cats, all values in pg/mg/min). Norepinephrine and dopamine significantly increased both the prostacyclin and the thromboxane release from venous tissue, while isoproterenol had no effect. Vasopressin significantly increased thromboxane release and decreased the ratio of prostacyclin vs. thromboxane production (from 10.4 +/- 1.6 to 7.5 +/- 1.6, in acetylsalicylic acid pretreated cats). Angiotensin and thrombin had no significant effects. Bradykinin (0.5 microgram/ml) significantly augmented prostacyclin release from venous tissue (14.4 +/- 2.6 from 10.9 +/- 2.4 pg/mg/min) and decreased thromboxane release (0.65 +/- 0.18 from 1.35 +/- 0.22 pg/mg/min). Methionine-enkephalin (5 micrograms/ml) significantly reduced the thromboxane release from venous tissue slices. The presented material demonstrates that several vasoactive agents modulate the vasoactive prostanoid release of the venous wall. In some cases, the prostacyclin and the thromboxane productions are influenced separately, which in turn will have its impact on smooth muscle activity and thrombocyte aggregation.     

Ozone-induced increase in exhaled 8-isoprostane in healthy subjects is resistant to inhaled budesonide

The aim of this study was to quantify lung oxidant stress after short-term ozone exposure as reflected by 8-isoprostane concentrations in exhaled breath condensate (EBC) and to investigate the effects of inhaled budesonide on this response. 8-Isoprostane is a prostaglandin-F(2 alpha) isomer that is formed in vivo by free radical-catalyzed peroxidation of arachidonic acid. EBC is a noninvasive method to collect airway secretions. We undertook a double-blind, randomized, placebo-controlled, crossover study with inhaled budesonide (800 microg) or placebo twice daily for 2 weeks prior to ozone exposure (400 parts per billion) for 2 h in nine healthy nonsmokers. Exhaled 8-isoprostane was measured by an enzyme immunoassay. 8-Isoprostane was increased 4 h after ozone exposure compared to pre-exposure values in both placebo (36.9 +/- 3.9 pg/ml, mean +/- SEM, vs. 16.9 +/- 0.7 pg/ml; p <.001) and budesonide groups (33.4 +/- 2.6 pg/ml vs. 15.8 +/- 0.3 pg/ml; p <.001). Pretreatment with budesonide did not affect the increases in 8-isoprostane (mean differences 3.4 pg/ml, 95% CI -8.9 to 15.7, p =.54). Short-term ozone exposure causes acute increase in lung oxidative stress as reflected by exhaled 8-isoprostane. This increase is resistant to pretreatment with a high dose of inhaled budesonide.     

Oleic acid lung injury increases plasma prostaglandin levels

To determine whether lung injury causes increased plasma prostaglandin (PG) levels, 35 rabbits received oleic acid and 35 served as controls. Half of each group also received 4 ml/kg of Intralipid over one hour and at least five in each subgroup received indomethacin 7.5 mg/kg. Arterial and venous plasma concentrations of PGE2, 6-keto-PGF1 alpha, and PGF2 alpha-M were measured. Venous PGE2 was significantly higher in the oleic acid-injured than in the normal lung group, 1560 +/- 270 (Mean +/- SEM) versus 880 +/- 140 pg/ml (p less than .05). Plasma levels were reduced by 50% with indomethacin, but PGE2 levels remained significantly higher than in the normal lung group, 850 +/- 180 versus 480 +/- 60 for arterial (p less than .05) and 820 +/- 140 versus 480 +/- 80 for venous (p less than .05), respectively. PGF2 alpha-M levels were significantly higher in the lung injury group, 240 +/- 50 versus 50 +/- 40 pg/ml for arterial (p less than .05) and 220 +/- 50 versus 95 +/- 40 for venous (p less than .05), respectively. These lung injury-related increases in PGE2 and PGF2 alpha-M appear related both to increased pulmonary production and to decreased pulmonary clearance. With Intralipid infusion, however, arterial PGE2 increased by 500 +/- 260 pg/ml compared to baseline (p less than .05) with no change in venous PGE2, indicating in this instance that the increase in arterial PGE2 levels is related to increased pulmonary production.     

Free-radical scavenging by Ouratea parviflora in experimentally-induced liver injuries

The antioxidant potential of crude extracts and fractions from leaves of Ouratea parviflora, a Brazilian medicinal plant used for the treatment of inflammatory diseases, was investigated in vitro through the scavenging of radicals 2-diphenyl-1-picryl-hydrazyl-hydrate (DPPH), hydroxyl radical (HO*), superoxide anion (O2*-), and lipid peroxidation in rat liver homogenate. The crude extract (CEOP) and hydro-alcoholic fraction (OP4) showed strong inhibitory activity toward lipid peroxidation induced by tert-butyl peroxide (IC50 = 2.3 +/- 0.2 and 1.9 +/- 0.1 microg/ml, respectively). The same products exhibited a strong concentration-dependent inhibition of deoxyribose oxidation (14.9 +/- 0.2 and 0.2 +/- 0.1 microg/ml, respectively), and also showed a considerable antioxidant activity against O2*- (87.3 +/- 0.1 and 73.1 +/- 0.4 microg/ml, respectively) and DPPH radicals (55.4 +/- 0.3 and 38.3 +/- 0.4 microg/ml, respectively). The protective effects of CEOP and OP4 were also studied in mouse liver. CCl4 significantly increased (by 90%) levels of lipid hydroperoxides, carbonyl protein content (64%), DNA damage index (133%), aspartate aminotransferase (261%), alanine aminotransferase (212%), catalase activity (23%), and also caused a decrease of 60% in GSH content. The results showed that CEOP and OP4 exerted cytoprotective effects against oxidative injury caused by CCl4 in rat liver, probably related to the antioxidant activity showed by the in vitro free radical scavenging property.     

Effects of vasomotor- and mediator-induced hypotension on bronchomotor tone in swine

We studied the sympathetic neural response on airways to hypotensive stimuli in 19 swine in vivo. The effects of pharmacologically induced hypotension with nitroprusside (NTP) and hypotension elicited by intravenous compound 48/80 (48/80), a mast cell degranulating agent, were compared after equivalent reductions in mean arterial blood pressure (MAP). Reduction of the MAP to 60% of base line with NTP in six swine caused an increase in plasma epinephrine (E) from 60 +/- 28 to 705 +/- 276 pg/ml (P = 0.032) and plasma norepinephrine (NE) from 270 +/- 46 to 796 +/- 131 pg/ml (P = 0.032). Comparable reduction in MAP elicited with 48/80 in six other swine caused a substantially greater increase in both plasma E (9,581 +/- 4,147 pg/ml; P = 0.012 vs. NTP group) and plasma NE (2,239 +/- 637 pg/ml; P = 0.041 vs. NTP group). Catecholamine secretion attenuated mediator-induced changes in lung resistance (RL). In animals receiving 48/80, RL increased from 2.97 +/- 0.31 to 7.44 +/- 0.56 cmH2O.l-1.s. In animals having ganglionic blockade with 7.5 mg/kg iv hexamethonium and beta-adrenergic blockade with propranolol (4.0 mg/kg iv followed by 40 micrograms/kg-1.min-1), comparable doses of 48/80 caused an increase in RL to 18.6 +/- 4.55 cmH2O.l-1.s (P less than 0.04 vs. swine receiving neither hexamethonium nor propranolol).(ABSTRACT TRUNCATED AT 250 WORDS)     

Spontaneous lipid peroxidation in rabbit and mouse epididymal spermatozoa: dependence of rate on temperature and oxygen concentration

The rate of spontaneous lipid peroxidation, as measured by formation of malonaldehyde (MA), was determined as a function of O2 concentration and temperature in mouse and rabbit spermatozoa released from the cauda epididymidis. The peroxidation rate was linear in O2 concentration in the suspending medium up to 210 microM (the concentration at PO2 of ambient air at 34 degrees C) for sperm from both species over the temperature range 34-40 degrees C. This is the range over which the reaction is measurable for both species: below 34 degrees C, the rates become too slow to be measured accurately for rabbit sperm by our methods, while above 40 degrees C the rates for mouse sperm become too rapid. This narrow range is characteristic of a high activation energy (EA) for the peroxidation process. Values of EA were calculated from plots of kox versus (T)-1, where kox is a second order rate constant with the units (10(8) cells/ml)-1 min-1. It is defined by the equation: vma = kox (Sp) (O2), where vma is the rate of malonaldehyde production, (Sp) is concentration of sperm cells and (O2) is the O2 concentration in the suspending medium. For mouse sperm, EA was calculated to 78.7 kcal/mol (329 KJ/mol); for rabbit sperm, the value was 77.6 kcal/ml (324 KJ/mol). These high EAs and consequent steep dependence of the spontaneous lipid peroxidation rates on temperature favor long sperm life in the epididymis at around 32 degrees C and low PO2 in these scrotal animals, while allowing for a relatively short life at 37 degrees C at higher PO2 in the oviduct.     

Pulmonary rapidly adapting receptors reflexly increase airway secretion in dogs

We attempted to determine whether stimulation of pulmonary rapidly adapting receptors (RARs) increase tracheal submucosal gland secretion in anesthetized open-chest dogs. Electroneurographic studies of pulmonary afferents established that RARs but not lung C-fibers were stimulated by intermittent lung collapse during deflation, collapse being produced by removing positive end-expiratory pressure (PEEP, 4 cmH2O) or by applying negative end-expiratory pressure (NEEP, -4 cmH2O). We measured tracheal secretion by the "hillocks" method. Removing PEEP or applying NEEP for 1 min increased secretion from a base line of 6.0 +/- 1.1 to 11.8 +/- 1.7 and 22.0 +/- 2.8 hillocks.cm-2.min-1, respectively (P less than 0.005). After PEEP was restored, dynamic lung compliance (Cdyn) was 37% below control, and secretion remained elevated (P less than 0.05). A decrease in Cdyn stimulates RARs but not other pulmonary afferents. Hyperinflation, which restored Cdyn and RAR activity to control, returned secretion rate to base line. Secretory responses to lung collapse were abolished by vagal cooling (6 degrees C), by pulmonary vagal section, or by atropine. We conclude that RAR stimulation reflexly increases airway secretion. We cannot exclude the possibility that reduced input from slowly adapting stretch receptors contributed to the secretory response.     

Concentration of aerosolized 99mTc-albumin in the pulmonary lymph of anesthetized sheep

We examined the lymphatic concentration of 99mTc-albumin deposited in the air spaces of anesthetized sheep to determine whether changes in the concentration reflected changes in lung epithelial function. Five control sheep were ventilated with an aerosol of 99mTc-albumin for 6 min, and the lung lymphatic concentration of the tracer was monitored for the next 2 h. During the last 45 min the lymphatic concentration stabilized at a value that was 0.03 +/- 0.01% of the estimated value in the air spaces. Pulmonary vascular hypertension, induced in seven sheep by increasing the left atrial pressure 20 cmH2O for 4 h, increased the lung lymph flow from a base-line value of 3 +/- 2 to 21 +/- 14 ml/h. This caused the concentration of the 99mTc-albumin in the lymph to double to 0.07 +/- 0.03% of the air space concentration (P less than 0.01). Lung injury induced by infusing 0.08-0.10 ml/kg oleic acid intravenously in seven other sheep increased the lymphatic concentration of the 99mTc-albumin 10-fold to 0.31 +/- 0.09% of the air space concentration (P less than 0.01). The increased tracer concentration in the sheep with pulmonary vascular hypertension could be the result of the increased lymph flow causing a diversion of tracer into the lymphatics. However, a mathematical model showed that the 10-fold increase in the lymphatic concentration in the sheep with lung injury was primarily the result of an increase in both permeability and surface area of the epithelium that participated in the transfer of the 99mTc-albumin from the air spaces into the lung tissue drained by the lymphatics.(ABSTRACT TRUNCATED AT 250 WORDS)     

Influence of tidal volume on pulmonary NO release,tissue lipid peroxidation and surfactant phospholipids

Mechanical stress during ventilation may cause or aggravate acute lung injury. This study investigates the influence of low vs. high tidal volume (V(t)) on factors known to play key roles in acute lung injury: nitric oxide release, eNOS and iNOS gene expression, lipid peroxidation (LPO), and surfactant phospholipids (PL). Isolated rabbit lungs were subjected to one of three ventilation patterns for 135 min (V(t)-PEEP): 6 ml/kg-0 cm H(2)O. 12 ml/kg-0 cm H(2)O 6 ml/kg-5 cm H(2)O, 12 ml/kg-0 cm H(2)O, and 6 ml/kg-5 cm H(2)O resulted in comparable peak inspiratory pressure (PIP). This allowed comparing low and high V(t) without dependence on PIP. Ventilatory patterns did not induce changes in pulmonary artery pressure, vascular permeability (K(f,c)), PIP or pulmonary compliance. High V(t) in comparison with both of the low V(t) groups caused an increase in BALF-nitrite (30.6+/-3.0* vs. 21.4+/-2.2 and 16.2+/-3.3 microM), BALF-PL (1110+/-19* vs. 750+/-68 and 634+/-82 microg/ml), and tissue LPO product accumulation (0.62+/-0.051* vs. 0.48+/-0.052 and 0.43+/-0.031 nmol/mg), *P<0.05 each. Perfusate nitrite and BALF-PL composition (assessed by use of 31P-NMR spectroscopy and MALDI-TOF mass spectrometry) did not differ among the groups. High V(t) ventilation reduced eNOS gene expression but did not affect iNOS expression. The increased release of NO and the accumulation of LPO products may represent early lung injury while elevated BALF-PL may reflect distension-induced surfactant secretion.