Prostaglandin E2 attenuation of sheep lung responses to endotoxin

Prostaglandin (PG) E2 can inhibit inflammatory responses of neutrophils and lymphocytes, including eicosanoid release. Diffuse lung injury after endotoxemia in sheep is accompanied by sequestration of neutrophils and lymphocytes in the lungs, and eicosanoids mediate some of the pathophysiology of the response. To determine whether exogenous PGE2 could prevent the endotoxin response, we measured pulmonary hemodynamics, gas exchange, and lung lymph responses to infusion of Escherichia coli endotoxin (0.5 micrograms/kg iv over 30 min) in unanesthetized sheep in the presence and absence of PGE2 (0.5 micrograms.kg-1.min-1) infused intravenously for 4 h beginning 0.5 h before endotoxin infusion. We also measured lung lymph concentrations of thromboxane B2 (TxB2) and prostacyclin metabolite, 6-keto-prostaglandin F1 alpha (6-keto-PGF1 alpha), by radioimmunoassay and leukotriene B4 (LTB4) by gas chromatography-mass spectrometry. PGE2 decreased endotoxin-induced pulmonary hypertension and hypoxemia and markedly attenuated the lymph flow and lymph protein clearance responses. PGE2 also attenuated endotoxin-induced increases in lung lymph TxB2 and 6-keto-PGF1 alpha and decreased lymph LTB4 flow after endotoxin without decreasing lymph LTB4 concentrations. We conclude that PGE2 infusion attenuates lung dysfunction caused by endotoxemia, possibly by preventing endogenous release of other eicosanoids.     

Lung eicosanoids in perinatal rats with congenital diaphragmatic hernia

Abnormal levels of pulmonary eicosanoids have been reported in infants with persistent pulmonary hypertension (PPH) and congenital diaphragmatic hernia (CDH). We hypothesized that a dysbalance of vasoconstrictive and vasodilatory eicosanoids is involved in PPH in CDH patients. The levels of several eicosanoids in lung homogenates and in bronchoalveolar lavage fluid of controls and rats with CDH were measured after caesarean section or spontaneous birth. In controls the concentration of the stable metabolite of prostacyclin (6-keto-PGF(1alpha)), thromboxane A(2) (TxB(2)), prostaglandin E(2) (PGE(2)), and leukotriene B(4) (LTB(4)) decreased after spontaneous birth. CDH pups showed respiratory insufficiency directly after birth. Their lungs had higher levels of 6- keto-PGF(1alpha), reflecting the pulmonary vasodilator prostacyclin (PGI(2)), than those of controls. We conclude that in CDH abnormal lung eicosanoid levels are present perinatally. The elevated levels of 6-keto-PGF(1alpha) in CDH may reflect a compensation mechanism for increased vascular resistance.     

Diethylcarbamazine on pulmonary vascular response to endotoxin in awake sheep

Diethylcarbamazine (DEC) is an inhibitor of lipoxygenase, with protective effects in several experimental models of anaphylaxis and lung dysfunction. The hypothesis of this study was that DEC would alter the pulmonary response to endotoxin infusion, especially the prolonged pulmonary hypertension, leukopenia, hypoxemia, and high flow of protein-rich lung lymph. We prepared sheep for chronic measurements of hemodynamics and collection of lung lymph. In paired studies we gave six sheep endotoxin (0.5 micrograms/kg iv) either with or without DEC. DEC was given (80-100 mg/kg iv) over 30 min followed by a continuous infusion at 1 mg X kg-1 X min-1. Endotoxin was given after the loading infusion of DEC, and variables were monitored for 4 h. The response to endotoxin was characterized by pulmonary hypertension, leukopenia, hypoxemia, and elevations of thromboxane B2 and 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha). Lymph flow and protein content reflected hemodynamic and permeability changes in the pulmonary circulation. DEC did not significantly modify the response to endotoxin by any measured variable, including pulmonary arterial and left atrial pressures, cardiac output, lymph flow and protein content, alveolar-to-arterial PO2 difference, blood leukocyte count, and lymph thromboxane B2 and 6-keto-PGF1 alpha. We could not find evidence of release of leukotriene C4/D4 by radioimmunoassay in lung lymph after endotoxin infusion with or without DEC treatment. We conclude that lipoxygenase products of arachidonic acid may not be a major component of the pulmonary vascular response to endotoxin.     

Dose-dependent effects of a pyridoquinazoline thromboxane synthetase inhibitor on arachidonic acid metabolites and hemodynamics during E. coli endotoxemia in anesthetized sheep

We investigated the effects of a new pyridoquinazoline thromboxane synthetase inhibitor infused before administering Escherichia Coli endotoxin into 18 anesthetized sheep with lung lymph fistulas. In normal sheep increasing plasma Ro 23-3423 concentrations were associated with increased plasma levels of 6-keto-PGF1 alpha, a reduced systemic vascular resistance (SVR, r = -0.80) and systemic arterial pressure (SAP, r = -0.92), the mean SAP falling from 80 to 50 mm Hg at the 20 and 30 mg/kg doses. Endotoxin infused into normal sheep caused transient pulmonary vasoconstriction associated with increased TxB2 and 6-keto-PGF1 alpha levels while vasoconstriction and TxB2 increase were significantly inhibited by pretreatment with Ro 23-3423 in a dose-dependent manner. When compared to controls, plasma and lymph levels of 6-keto-PGF1 alpha, PGF2 alpha and PGE2 after endotoxin infusion were increased several-fold by administering Ro 23-3423 up to plasma levels of 10 micrograms/ml. Doses over 30 mg/kg with blood levels above 10 micrograms/ml reduced plasma and lymph levels of 6-keto-PGF1 alpha, PGF2 alpha and PGE2, suggesting cyclooxygenase blockade at this dose. The peak 6-keto-PGF1 alpha levels at 60 min after endotoxin infusion in sheep with Ro-23-3423 levels below 10 micrograms/ml were associated with the greatest systemic hypotension due to a reduced SVR (r = -0.86). After endotoxin infusion the leukotrienes B4, C4, D4 and E4 in lung lymph were assayed by radioimmunoassay and high pressure liquid chromatography and remained at baseline values.     

Release of prostaglandins and thromboxanes by guinea pig isolated type II pneumocytes

Lung cells have been isolated by enzymatic digestion of guinea pig lungs and mechanical dispersion to obtain a suspension of viable cells (approximately 500 X 10(6) cells). Type II pneumocytes have been purified to approximately 92% by centrifugal elutriation (2000 rpm, 15 ml/min) followed by a plating in plastic dishes coated with guinea pig IgG (500 micrograms/ml). We have investigated the arachidonic acid metabolism through the cyclooxygenase pathway in this freshly isolated type II cells (2 x 10(6) cells/ml). Purified type II pneumocytes produced thromboxane B2 (TxB2) predominantly and to a smaller extent the 6-keto prostaglandin PGF1 alpha (6-keto-PGF1 alpha) and prostaglandin E2 (PGE2) after incubation with 10 microM arachidonic acid. The stimulation of pneumocytes with 2 microM calcium ionophore A23187 released less eicosanoids than were produced when cells were incubated with 10 microM arachidonic acid. There was no additive effect when the cells were treated with both arachidonic acid and the ionophore A23187. Guinea pig type II pneumocytes failed to release significant amounts of TxB2, 6-keto-PGF1 alpha and PGE2 after stimulation with 10 nM leukotriene B4, 10 nM leukotriene D4, 10 nM platelet-activating factor, 5 microM formyl-methionyl-leucyl-phenylalanine, 0.2 microM bradykinin and 10 nM phorbol myristate acetate. Our findings indicate that guinea pig type II pneunomocytes possess the enzymatic machinery necessary to convert arachidonic acid to specific cyclooxygenase products, which may suggest a role for these cells in lung inflammatory processes.     

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.     

Effect of LY171883 on endotoxin-induced lung injury in pigs

We evaluated the role of sulfidopeptide leukotrienes as mediators of endotoxin-induced respiratory failure in pigs. Escherichia coli endotoxin (055-B5) was infused intravenously into anesthetized 10- to 14-wk-old pigs at 5 micrograms/kg the 1st h followed by 2 micrograms.kg-1.h-1 for 3 h in the presence and absence of LY171883, a specific leukotriene D4 (LTD4)/LTE4 receptor antagonist. Endotoxin caused hemoconcentration, granulocytopenia, decreased cardiac index, systemic hypotension, pulmonary hypertension, increased pulmonary vascular resistance, bronchoconstriction, hypoxemia, increased permeability of the alveolar-capillary membrane, pulmonary edema, and increased plasma concentrations of thromboxane B2 (TxB2), prostaglandin F2 alpha (PGF2 alpha), and 6-keto-PGF1 alpha. LY171883 did not modify endotoxin-induced cardiopulmonary and hematologic abnormalities, except for a modest attenuation of pulmonary hypertension (at 1 h) and increased pulmonary vascular resistance (at 1-2 h). Ex vivo stimulation of whole blood with calcium ionophore caused large increases in plasma concentrations of TxB2, PGF2 alpha, and LTB4. These increases were not significantly modified in blood derived from pigs treated with LY171883, indicating no inhibition of cyclooxygenase or 5-lipoxygenase. We conclude that LTD4 and LTE4 are not important mediators of endotoxin-induced lung injury in anesthetized pigs, although they may contribute modestly to pulmonary vasoconstriction.     

Calcium ionophore (A-23187) induced peritoneal eicosanoid biosynthesis: a rapid method to evaluate inhibitors of arachidonic acid metabolism in vivo

The present investigation characterizes calcium ionophore (A-23187) induced peritoneal eicosanoid biosynthesis in the rat. Intraperitoneal injection of A-23187 (20 mug/rat) stimulated marked biosynthesis of 6-keto-PGF(1alpha) (6-KPA), TxB(2), LTC(4) and LTB(4), with no detectable changes on levels of PGE(2). Levels of all eicosanoids decreased rapidly after a peak which was seen as early as 5 min. Enzyme markers of cellular contents of neutrophils and mononuclear cells, MPO and NAG respectively, decreased rapidly after ionophore injection; this was followed by increases after 60 min. Indomethacin, a selective cyclooxygenase inhibitor, and zileuton and ICI D-2138, two selective 5-lipoxygenase inhibitors attenuated prostaglandin and leukotriene pathways respectively. Oral administration of zileuton (20 mg/kg, p.o.) inhibited LTB(4) biosynthesis for up to 6 h suggesting a long duration of pharmacological activity in the rats consistent with its longer half-life. The rapid onset and the magnitude of increases in levels of eicosanoids render the ionophore induced peritoneal eicosanoid biosynthesis a useful model to evaluate pharmacological profiles of inhibitors of eicosanoid pathways in vivo.     

Effect of endotoxemia on hypoxic pulmonary vasoconstriction in unanesthetized sheep

This study examined the effect of acute endotoxemia on hypoxic pulmonary vasoconstriction (HPV) in awake sheep. Thirteen sheep were chronically instrumented with Silastic catheters in the pulmonary artery, left atrium, jugular vein, and carotid artery; with a Swan-Ganz catheter in the main pulmonary artery; with a chronic lung lymph fistula; and with a tracheostomy. Base-line HPV was determined by measuring the change in pulmonary vascular resistance (PVR) while sheep breathed 12% O2 for 7 min. Concentrations of immunoreactive 6-keto-PGF1 alpha and thromboxane B2 (TXB2) were measured in lung lymph during the hypoxic challenge. Escherichia coli endotoxin (0.2-0.5 micrograms/kg) was infused intravenously. Four hours after endotoxemia, HPV was measured. In five sheep, meclofenamate was infused at 4.5 h after endotoxemia and HPV measured again. During the base-line hypoxic challenge, PVR increased by 36 +/- 9% (mean +/- SE). There was no significant change in lung lymph 6-keto-PGF1 alpha or TXB2 levels with hypoxia. Twelve of the 13 sheep showed a decrease in HPV 4 h after endotoxemia; the mean change in PVR with hypoxia was -8 +/- 5%, which was significantly (P less than 0.05) reduced compared with base-line HPV. The infusion of meclofenamate at 4.5 h after endotoxin did not restore HPV.     

Effects of thromboxane synthase inhibition on air emboli lung injury in sheep

We tested the effects of OKY-046, a thromboxane synthase inhibitor, on lung injury induced by 2 h of pulmonary air infusion (1.23 ml/min) in the pulmonary artery of unanesthetized sheep with chronic lung lymph fistula so as to assess the role of thromboxane A2 (TxA2) in the lung injury. We measured pulmonary hemodynamic parameters and the lung fluid balance. The concentrations of thromboxane B2 (TxB2) and 6-ketoprostaglandin F1 alpha (6-keto-PGF1 alpha) in plasma and lung lymph were determined by radioimmunoassay. Air infusion caused sustained pulmonary hypertension and an increase in pulmonary vascular permeability. The levels of TxB2 and 6-keto-PGF1 alpha in both plasma and lung lymph were significantly elevated during the air infusion. TxB2 concentration in plasma obtained from the left atrium was higher than that from the pulmonary artery at 15 min of air infusion. When sheep were pretreated with OKY-046 (10 mg/kg iv) prior to the air infusion, increases in TxB2 were prevented. The pulmonary arterial pressure, however, increased similarly to that of untreated sheep (1.8 X base line). The increase in lung lymph flow was significantly suppressed during the air infusion. Our data suggest that the pulmonary hypertension observed during air embolism is not caused by TxA2.     

Human recombinant tumor necrosis factor alpha infusion mimics endotoxemia in awake sheep

The macrophage-derived cytokine tumor necrosis factor alpha (TNF alpha) has been proposed as the major mediator of endotoxin-induced injury. To examine whether a single infusion of human recombinant TNF alpha (rTNF alpha) reproduces the pulmonary effects of endotoxemia, we infused rTNF alpha (0.01 mg/kg) over 30 min into six chronically instrumented awake sheep and assessed the ensuing changes in hemodynamics, lung lymph flow and protein concentration, and number of peripheral blood and lung lymph leukocytes. In addition, levels of thromboxane B2, 6-ketoprostaglandin F1 alpha, prostaglandin E2, and leukotriene B4 were measured in lung lymph. Pulmonary arterial pressure (Ppa) peaked within 15 min of the start of rTNF alpha infusion [base-line Ppa = 22.0 +/- 1.5 (SE) cmH2O; after 15 min of rTNF alpha infusion, Ppa = 54.2 +/- 5.4] and then fell toward base line. The pulmonary hypertension was accompanied by hypoxemia and peripheral blood and lung lymph leukopenia, both of which persisted throughout the 4 h of study. These changes were followed by an increase in protein-rich lung lymph flow (base-line lymph protein clearance = 1.8 +/- 0.4 cmH2O; 3 h after rTNF alpha infusion, clearance = 5.6 +/- 1.2), consistent with an increase in pulmonary microvascular permeability. Cardiac output and left atrial pressure did not change significantly throughout the experiment. Light-microscopic examination of lung tissue at autopsy revealed congestion, neutrophil sequestration, and patchy interstitial edema. We conclude that rTNF alpha induces a response in awake sheep remarkable similar to that of endotoxemia. Because endotoxin is a known stimulant of TNF alpha production, TNF alpha may mediate endotoxin-induced lung injury.     

Thromboxane A2 and prostacyclin do not modulate pulmonary hemodynamics during exercise in sheep

The purpose of this study was to determine the role of thromboxane and prostacyclin in modulating pulmonary hemodynamics during maximal cardiopulmonary stress in the healthy lung. We studied 11 yearling sheep in paired studies during progressive maximal treadmill exercise with and without meclofenamate (n = 5), ibuprofen (n = 6), or UK38485 (n = 2). We also studied five sheep during hypoxia and hypoxic exercise, and six sheep during prolonged steady-state treadmill exercise for 45-60 min with and without drug treatment. We measured the metabolites of thromboxane A2 (thromboxane B2, TxB2) and prostacyclin (6-ketoprostaglandin F1 alpha, 6-keto-PGF1 alpha) in blood plasma and lung lymph in each protocol. We found that progressive exercise significantly reduced pulmonary vascular resistance but that cyclooxygenase or thromboxane synthesis blockade did not alter the change. Plasma TxB2 rose minimally but significantly during maximal exercise, but 6-keto-PGF1 alpha did not change. During continuous hypoxia, exercise reduced pulmonary vascular resistance nearly to base-line levels, but the degree of reduction was also unchanged by drug treatment. There were also no significant changes in lymph or plasma TxB2 or 6-keto-PGF1 alpha during 45-60 min of continuous moderate exercise. We conclude that neither TxB2 nor prostacyclin modulate pulmonary hemodynamics in the normal lung during maximal exercise, prolonged moderate exercise, or exercise-induced reductions in vascular resistance during hypoxia.     

Low-dose PGI2 prevents monocrotaline-induced thromboxane production and lung injury

In animals, monocrotaline induces an acute lung injury secondary to capillary endothelial damage. To date, no reports have appeared dealing with the role of prostaglandins in monocrotaline-induced injury. Our studies, in dogs, revealed that monocrotaline (30 mg/kg iv) caused an acute and persistent thrombocytopenia, lung platelet deposition, pulmonary hypertension, and increased extravascular lung water (EVLW). The pulmonary hypertensive response was biphasic. Thromboxane B2 levels were similarly biphasic, peaking at 5 min and 2 h. The levels of 6-keto-PGF1 alpha peaked at 30 min and returned to base line at 3 h. Pulmonary vascular resistance paralleled thromboxane levels. Infusion of prostacyclin (PGI2) at 50 ng X kg-1 X min-1 effectively prevented the thrombocytopenia, lung platelet deposition, pulmonary hypertension, and increased EVLW; and it decreased excess thromboxane production by 79%. These results suggest that platelet activation and lung sequestration play a role in acute lung injury due to monocrotaline, and that the resultant thromboxane production may contribute to the pulmonary hypertension. PGI2 ameliorates monocrotaline-induced injury, perhaps by preventing platelet activation.     

Effects of acute and chronic ethanol administration on thromboxane and prostacyclin levels and release in rat brain cortex

The effects of acute (3 g/kg i.p. two hours before sacrifice) and chronic (6% in drinking water and libitum for 15 days) ethanol administration to male rats (200 g body weight) on basal levels and release of TxB2 and 6-keto-PGF1 alpha in brain cortex were studied. Also the effects of chronic ethanol (30 days) on the fatty acid composition of brain cortical tissue and liver phospholipids were investigated. Acute treatment reduced basal levels of 6-keto- PGF1 alpha in brain cortical tissue (rats sacrificed by microwave radiation) and decreased the accumulation of 6-keto-PGF1 alpha in brain cortex after post-decapitation ischemia (PDI). Basal TxB2 levels were also reduced in brain cortex, but TxB2 release during PDI was enhanced. Chronic treatment (15 days) induced changes of TxB2 and 6-keto-PGF1 alpha levels and release during PDI in brain cortex less pronounced than those observed after acute treatment. The reduced effectiveness of chronic ethanol on brain vasoactive eicosanoids suggest adaptation processes. After chronic treatment (30 days), the fatty acid composition of brain cortex total phospholipids were not significantly modified. Changes of eicosanoid production after ethanol were thus independent from modifications of the fatty acid precursor pool(s). Ethanol-induced changes in the production of vascular eicosanoids in the CNS may be of relevance to the action of the compound on the CNS and may also have implications for the clinic.     

Chronic administration of ethyl docosahexaenoate reduces gerbil brain eicosanoid productions following ischemia and reperfusion

Arachidonic acid (AA) and its vasoactive metabolites have been implicated in the pathogenesis of brain damage induced by cerebral ischemia. The membrane AA concentrations can be reduced by changes in dietary fatty acid intake. The purpose of the present study was to investigate the effects of chronic ethyl docosahexaenoate (E-DHA) administration on the generation of eicosanoids of AA metabolism during the period of reperfusion after ischemia in gerbils. Weanling male gerbils were orally pretreated with either E-DHA (100, 200 mg/kg) or vehicle, once a day, for 10 weeks, and subjected to transient forebrain ischemia by bilateral common carotid occlusion for 10 min. E-DHA (200 mg/kg) pretreatment significantly decreased the content of brain lipid AA at the termination of treatment, prevented postischemic impaired regional cerebral blood flow (rCBF) and reduced the levels of brain prostaglandin (PG) PGF(2alpha) and 6-keto-PGF(1alpha), and thromboxane B(2) (TXB(2)), as well as leukotriene (LT) LTB(4) and LTC(4) at 30 and 60 min of reperfusion compared with the vehicle, which was well associated with the attenuated cerebral edema in the E-DHA-treated brain after 48 h of reperfusion. These data suggest that the E-DHA (200 mg/kg) pretreatment reduces the postischemic eicosanoid productions, which may be due to its reduction of the brain lipid AA content.     

Does thromboxane mediate the indirect contractile action of leukotriene D4 in guinea-pig isolated lung parenchyma under equilibrium conditions?

The role that thromboxane A2 plays in contractions induced by leukotriene D4 in guinea-pig isolated lung parenchyma was investigated under equilibrium conditions. Lung tissue generated thromboxane A2 and prostacyclin spontaneously as evidenced by the slow accumulation of their biologically inactive metabolites, thromboxane B2 and 6-keto-prostaglandin F1 alpha, in the bathing buffer. Challenge of guinea-pig lung parenchyma with a high concentration (EC90 for tension generation) of leukotriene D4 (200 nM) produced a biphasic contraction of the tissue that consisted of an initial rapid increase in isometric tension followed by a slowly developing, well-sustained contracture. In addition, leukotriene D4 (200 nM) effected a transient increase (over basal) in the generation of thromboxane A2 and prostacyclin that lagged significantly behind the tension response. Kinetic analysis of the mechanical and eicosanoid-generating effect of leukotriene D4 revealed that tension development could be suitably fitted to a biexponential function, whilst the release of both eicosanoids from the lung occurred monoexponentially. Pretreatment of the lung with the cyclooxygenase inhibitor, flurbiprofen, which effectively abolished both the spontaneous and the leukotriene D4-stimulated eicosanoid biosynthesis, significantly reduced both the first order rate coefficient of the first exponent and the maximum amplitude of this function with respect to control. This change in the kinetics describing leukotriene D4-induced contractions was explained by the fact that the initial rate of tension development was markedly reduced following pretreatment of the lung with flurbiprofen. Neither the inhibitor of thromboxane synthetase, dazmegrel, which selectively inhibited (by 95%) leukotriene D4-stimulated thromboxane A2 formation, nor blockade of 11 alpha,9 alpha-epoxymethano-prostaglandin H2 (U-46619)-sensitive (thromboxane A2) receptors with either AH 23848 or EP 092 affected the profile of leukotriene D4-induced tension development in guinea-pig lung. It is concluded that a high concentration of leukotriene D4 (200 nM) contracts guinea-pig lung by both a direct and indirect mechanism. Initially, a rapid short-lived contraction of the lung is manifest which is dependent, in part, upon the synthesis and release of cyclooxygenase product(s) other than thromboxane A2. This initial response occurs coincidently with, and is subsequently followed by, the development of a tonic well-sustained contracture that is the result of a direct action of leukotriene D4 on the contractile cells that comprise the lung.     

Eicosanoid balance and perfusion redistribution of oleic acid-induced acute lung injury.

We have proposed that endogenous prostacyclin opposes the vasoconstriction responsible for redistribution of regional pulmonary blood flow (rPBF) away from areas of increased regional lung water concentration (rLWC) in canine oleic acid- (OA) induced acute lung injury (D. P. Schuster and J. Haller. J. Appl. Physiol. 69: 353-361, 1990). To test this hypothesis, we related regional lung tissue concentrations of 6-ketoprostaglandin (PG) F1 alpha and thromboxane (Tx) B2 in tissue samples obtained 2.5 h after administration of OA (0.08 ml/kg iv) to rPBF and rLWC measured by positron emission tomography. After OA only (n = 16), rLWC increased in dependent lung regions. Some animals responded to increased rLWC by redistribution of rPBF away from the most edematous regions (OA-R, n = 6), whereas others did not (OA-NR, n = 10). In another six animals, meclofenamate was administered after OA (OA-meclo). After OA, tissue concentrations of 6-keto-PGF1 alpha were greater than TxB2 in all groups, but concentrations of 6-keto-PGF1 alpha were not different between OA-R and OA-NR animals. TxB2 was increased in the dependent regions of animals in both OA-R and OA-NR groups compared with controls (no OA, n = 4, P < 0.05). The tissue TxB2/6-keto-PGF1 alpha ratio was smaller in controls and OA-NR in which no perfusion redistribution occurred than in OA-R and OA-meclo in which it did occur. This TxB2/6-keto-PGF1 alpha ratio correlated significantly with the magnitude of perfusion redistribution.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effect of arachidonic acid-rich oil on lipids and arachidonate metabolites in ethanol- treated rats.

The effects of dietary arachidonic acid-rich oil (AAoil) on lipids and arachidonate metabolites in the liver and plasma were evaluated in ethanol-treated rats. Rats were fed a purified diet containing 10% weight of lard or AAoil for 14 days. Ethanol was administered by gavage at a single daily dose of 3 g/kg body weight. Comparing with the lard group, a decrease was observed in liver fatty vacuoles in the AAoil group. Plasma 6-keto-prostaglandin (PG) F1 alpha and thromboxane (TX) B(2)levels and the 6-keto-PGF1 alpha/TXB(2)ratio increased significantly in the AAoil group. Liver 6-keto-PGF1 alpha also increased but not leukotriene B(4)in the AAoil group. In the phospholipid fraction of liver tissue, plasma and red blood cells, arachidonic acid (20:4n-6) and docosatetraenoic acid (22:4n-6) increased and oleic acid (18:1n-9) and linoleic acid (18:2n-6) decreased significantly in the AAoil group compared with the lard group. These observations suggest that AAoil supplementation reduces liver injury of ethanol-treated rats, although longer observation will be necessary for confirmation.     

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)     

Analysis of 6-keto PGF1 alpha, 5-HETE, and LTC4 in rat lung: comparison of GM/MS, RIA, and EIA

The recent availability of fast and sensitive radioimmunoassay (RIA) and enzyme immunoassay (EIA) procedures to measure icosanoids has led to utilization of these techniques by many investigators. A major concern has been that techniques based on immunoreactivity may lack specificity, in particular if complex biologic fluids or tissue extracts are evaluated. The purpose of this investigation was the comparison of icosanoid measurements obtained either with EIA or RIA with those obtained by gas chromatography/mass spectrometry (GC/MS). Rats were injected with Salmonella enteritidis endotoxin, killed at various times after the injection and the lung extract assayed for 6-keto-PGF1 alpha, 5-HETE and LTC4. By EIA lung tissue was found to contain large quantities of 6-keto-PGF1 alpha after endotoxin stimulation. Comparisons made between EIA and GC/MS analysis showed good correlation between 6-keto-PGF1 alpha amounts in lung as determined by each technique. It was also determined that little purification of lung extract was needed to obtain reliable quantitation of 6-keto-PGF1 alpha, probably due to the specificity of the antibody and the large quantity of this prostaglandin produced. Crudely purified (Sep-Pak) lung extracts gave 5-HETE levels by RIA which were highly correlated with GC/MS values, but RIA values were 70% higher than those obtained by GC/MS. The presence of other components in lung extract which cross react with this 5-HETE antibody was probably responsible for the higher values obtained by RIA. LTC4 was measured by immunoassay in crude lung extracts, as well as after Sep-Pak purification and HPLC purification. LTC4 levels were identical in unpurified lung extract and after Sep-Pak purification, but decreased substantially after HPLC purification. Thus, by validating the icosanoid immunoassays, we have found that they can give accurate and reproducible results in lung tissue, although LTC4 and 5-HETE must be purified prior to analysis.