Effect of endotoxin on the integrity of the peripheral (soft tissue) microcirculation

Peripheral edema, hypoproteinemia, and increased fluid requirements are characteristically seen with sepsis. Our purpose was to determine whether the soft tissue edema is caused by a direct vascular injury from sepsis or is secondary to hypoproteinemia. We determined the effect of endotoxin on peripheral (soft tissue) microvascular integrity using lymph flow (QL) and lymph/plasma (L/P) protein ratio to reflect fluid flux and increased permeability. Response was compared with that seen in the lung. Fourteen unanesthetized sheep were given intravenous E. coli endotoxin 2 micrograms/kg. Vascular pressures and cardiac output (CO) were maintained constant with the necessary fluid infusion. Lung QL increased two- to fourfold in all animals with lymph being protein-rich, indicating increased permeability. Peripheral QL increased transiently in response to an initial increase in vascular pressure returning rapidly to baseline except in those animals (N = 5) demonstrating hypoproteinemia where QL remained increased by 50 to 75%. The increased QL was totally explained by the degree of protein depletion, with no evidence of increased permeability. To assure an adequate endotoxin exposure to the peripheral microvessels, endotoxin (2 micrograms/kg) was also directly injected into the tissue drained by the soft tissue lymphatic. We noted a characteristic endotoxin pulmonary hypertension phase but, again, no increase in peripheral microvascular permeability was found. We conclude that endotoxemia does not alter peripheral microvascular permeability if tissue perfusion is maintained, while the lung is clearly a target organ. Hypoproteinemia may be responsible for the early edema in soft tissues with sepsis.     

Relationship between the lung and systemic response to endotoxin: comparison of physiologic change and the degree of lipid peroxidation.

The lung and systemic response to Escherichia coli endotoxin either 2 or 5 micrograms/kg was measured in 16 sheep with chronic lung and soft tissue lymph fistulae. Oxidant-induced lung and liver lipid peroxidation was measured as tissue malondialdehyde (MDA). Conjugated dienes were also monitored. Both doses produced a comparable pulmonary hypertension and hypoxia as well as a comparable increase in protein-rich lymph flow, QL. However, lung MDA was significantly greater with the 5 micrograms/kg than with the 2 micrograms/kg dose, both being more than twofold greater than controls. The systemic physiologic responses between the two doses were quite different. The 5 microgram/kg dose resulted in a significant increase in oxygen delivery (DO2), oxygen consumption (VO2), and decrease in arterial O2 extraction in the 3-5 hr postendotoxin period compared with the 2 microgram/kg dose. A twofold increase in protein-rich soft tissue QL was also seen after the 5 micrograms/kg dose, whereas QL was not changed after 2 micrograms/kg. Liver MDA was only increased by 30% over controls with both doses. We conclude that the relationship between oxidant change and physiologic response varies considerably between lung and systemic tissues after endotoxemia with the degree of lung lipid peroxidation corresponding with the degree of impairment in systemic tissue O2 extraction and the onset of delivery-dependent O2 consumption.     

Dibutyryl cyclic AMP attenuates lung responses induced by endotoxin in conscious sheep.

Dibutyryl cyclic AMP (DBcAMP) could inhibit the production of prostanoids and modulate the pulmonary vascular responses induced by endotoxin. Diffuse lung injury after endotoxemia in sheep is accompanied by the production of prostanoids and an increase in endothelial permeability. To determine whether exogenous DBcAMP could prevent the endotoxin responses, we measured pulmonary hemodynamics, gas exchange, and lung lymph responses to an intravenous infusion of Escherichia coli endotoxin (1.0 micrograms/kg over 30 min) in unanesthetized sheep in the presence and absence of DBcAMP (30 micrograms/kg/min) infused intravenously for 6 h beginning 1 h before endotoxin infusion or for 4.5 h after 30 min of treatment with endotoxin infusion. We also measured circulating leukocytes and lung lymph and plasma concentrations of thromboxane B2 (TXB2) and prostacyclin (6-keto-PGF1 alpha) metabolites by radioimmunoassay. DBcAMP infusion before endotoxin infusion decreased endotoxin-induced pulmonary hypertension and hypoxemia and markedly attenuated the increased lung lymph flow and lymph protein clearance. DBcAMP after endotoxin only attenuated the increased lung lymph flow and lymph protein clearance. DBcAMP treatment both before and after endotoxin infusion blocked endotoxin-induced increases in lung lymph and plasma TXB2 and 6-keto-PGF1 alpha. DBcAMP did not affect the number of circulating leukocytes. Although DBcAMP alone did not affect the pulmonary and systemic hemodynamics and lung lymph balance, the potential that DBcAMP directly modulates the pulmonary vascular responses to endotoxin as a vasodilator could be expected. We conclude that DBcAMP infusion attenuates lung dysfunction caused by endotoxemia, possibly by preventing prostanoid release and modulating the pulmonary vascular responses.     

Pentafraction reduces the lung lymph response after endotoxin administration in the ovine model.

For the past half-century, several high molecular weight compounds have been used for volume expansion during cardiopulmonary resuscitation. However, the effectiveness and side effects of these different expanders are varied. We have compared plasma, pentastarch, and a new product, pentafraction, for effective plasma volume expansion before and after tissue injury with endotoxin administration. In each group, eight range ewes instrumented with a Swan-Ganz, arterial, and venous catheters, and lung and flank lymphatic cannulas were compared. Each group received 15 ml/kg of either 6% pentafraction, 6% pentastarch, or plasma followed two hours later by 1.5 micrograms/kg/0.5 hr E. Coli endotoxin over 30 min. Data were collected for an additional 24 hr after endotoxin administration. Our results indicated a plasma volume expansion in all three groups. However, the prior administration of pentafraction significantly attenuated the increase in the lung lymph flow and early evaluation of systemic vascular resistance noted with endotoxin in comparison to the other two groups.     

Increased sheep lung vascular permeability caused by Escherichia coli endotoxin.

We infused Escherichia coli endotoxin, 0.07-1.33 microgram/kg, intravenously into chronically instrumented unanesthetized sheep and measured pulmonary arterial and left atrial pressures, lung lymph flow, lymph and blood plasma protein concentrations, and arterial blood gases. Endotoxin caused a biphasic reaction: an early phase of pulmonary hypertension and a long late phase of steady state increased pulmonary vascular permeability during which pulmonary arterial and left atrial pressures were not increased significantly and lung lymph flow was 5 times the baseline value. Lymph: plasma total protein concentration ratio during the late phase (0.76 +/- 0.04) was significantly (P less than 0.05) higher than during baseline (0.66 +/- 0.03). The lymph response was reproducible. Lung lymph clearance of endogenous proteins with molecular radii (r) 35.5 to 96 A was increased during the steady state late phase of the reaction, but, as during baseline, clearance decreased as r increased. The endotoxin reaction was similar to the reaction to infusing whole Pseudomonas bacteria, except that endotoxin had less effect on pressures during the steady state response and caused a relatively larger increase in lymph clearance of large proteins. We conclude that E. coli endotoxin in sheep causes a long period of increased lung vascular permeability and may have a greater effect on large solute pathways across microvessels than do Pseudomonas bacteria.     

Relationship of increased lung serotonin levels to endotoxin-induced pulmonary hypertension in sheep. Effect of a serotonin antagonist

A persistent pulmonary artery hypertension, increased airways resistance, increased vascular permeability to protein, and hypoxia are characteristic of sepsis-induced ARDS in humans and are present in the late phase injury response seen in sheep after endotoxin. Our purpose was to determine the role of serotonin, 5-HT, in the steady-state pulmonary hypertension and decreased arterial oxygen tension seen beginning approximately 3 h after Escherichia coli endotoxin injury (2 micrograms/kg) in the adult sheep. Plasma 5-HT levels remained constant, whereas lung lymph values increased from a baseline of 60 +/- 40 to 180 +/- 70 and 270 +/- 90 ng/ml at 1-h and at 3- to 5-h periods, respectively, after endotoxin. Platelet count decreased significantly only at the 3-h time period. Ketanserin, a 5-HT antagonist, was infused (0.15 mg/kg/h) in 7 sheep during endotoxin injury. The degree of early pulmonary hypertension and hypoxia was not affected by ketanserin. Mean values for pulmonary artery pressure and arterial oxygen tension were 40 +/- 8 mmHg and 70 +/- 8 torr for endotoxin alone and 38 +/- 7 mmHg and 72 +/- 7 torr for the ketanserin group. Steady-state, protein-rich pulmonary perfusion was also not altered, being increased 3-fold in both groups. Pulmonary hypertension and hypoxia were significantly attenuated, however, at the 3- to 5-h period with ketanserin, compared with endotoxin alone, the pulmonary artery pressure decreasing from 29 +/- 5 to 22 +/- 4 mmHg and the PaO2 increasing from 75 +/- 4 to 83 +/- 5 torr.(ABSTRACT TRUNCATED AT 250 WORDS)     

TNF- and LPS-induced changes of lung vascular permeability: studies in unanesthetised sheep

There have been reports that the administration of TNF produces many of the cardiopulmonary changes seen with endotoxin (LPS). We asked whether all of LPS effects can be mimicked by TNF infusion. The effects of infusion of (human recombinant) TNF (50 micrograms/kg/30 min) and LPS (3 micrograms/kg/30 min) on permeability characteristics of sheep lungs were compared. Thirteen sheep were chronically instrumented for cardiopulmonary studies including lung lymph data. Infusion of LPS and TNF result in an increase of body temperature and lung lymph protein clearance (measured as the product of Lymph Flow and Lymph/Plasma Protein Ratio). The two responses had entirely different time courses. This might be related to the significantly longer period of pulmonary hypertension (MPAP) with LPS, which was only transient with TNF. Similar differences in plasma levels of thromboxane B2 (TxB2) were also noted. There were also differences in leukocyte kinetics, arterial blood gases, and plasma lactate levels. This indicates that although TNF infusion results in an increased pulmonary microvascular permeability, this event occurs without concomitant changes in thromboxane metabolism and exhibits time characteristics somewhat different from endotoxin.     

A 21-aminosteroid, U-74006F, attenuates endotoxin-induced lung injury in awake sheep

The purpose of the present study was to examine the efficacy of U-74006F, a 21-aminosteroid, on lung dysfunction induced by endotoxaemia in awake sheep with lung lymph fistula and haemodynamic monitoring. We measured pulmonary haemodynamics, lung lymph balance, circulating leucocyte count, arterial blood gas tensions, and levels of thromboxane (Tx) B2 and 6-keto-prostaglandin (PG) F1 alpha in plasma and lung lymph. We performed two experiments. In experiment 1 (n = 6), we intravenously infused Escherichia coli lipopolysaccharide endotoxin (1 microgram/kg) over 30 min and observed the parameters over 5 h. In experiment 2 (n = 6), we pretreated sheep with an intravenous bolus of U-74006F (2 mg/kg) 30 min before the infusion of endotoxin in the same manner of experiment 1, and continuously infused U-74006F (0.5 mg/kg per h) over 5 h after the bolus during the experiment. The U-74006F significantly suppressed the early pulmonary hypertension, the late increase in pulmonary permeability and the elevations of TxB2 and 6-keto-PGF1 alpha levels in plasma and lung lymph during the early period following endotoxaemia, although the compound did not change the time course of leucocytopenia and hypoxaemia. These findings suggest that the administration of U-74006F attenuates the lung dysfunction induced by endotoxaemia in awake sheep.     

Effects of continuous infusion of nitroglycerin on pulmonary hemodynamics, lung lymph balance, and prostanoid products in the response to endotoxin in awake sheep

We examined the effects of continuous intravenous infusion of nitroglycerin (NTG) on lung dysfunction induced by endotoxemia in awake sheep chronically instrumented with lung lymph fistula. We measured the responses of hemodynamics, lung lymph balance, and thromboxane (Tx)B₂ and 6-keto-prostaglandin (PG) F1α levels in plasma and lung lymph to endotoxin administration (1 μg/kg, intravenously [IV], over 30 min) with and without continuous infusion of NTG (1 μg/kg/min). Continuous infusion of NTG alone (n=5) over 5 hr did not significantly alter systemic, pulmonary hemodynamics, and/or lung lymph fluid filtration. Infusion of endotoxin alone (n=7) caused remarkable increases in pulmonary artery pressure (Ppa) and lung lymph flow ( Qlym) in the early phase. Continuous infusion of NTG (n=6) significantly prevented the early increases in Ppa and Qlym after endotoxin. The increased values of TxB₂ and 6-keto-PGF_1α in both plasma and lung lymph after endotoxemia showed the same increases in groups with and without NTG. These findings suggest that the reduction of pulmonary artery pressure induced by NTG decreased the filtration of fluid into the lungs associated with endotoxemia in sheep, and that the mechanism of vasodilating action of NTG is not due to modifications of constrictive-dilated cyclo-oxygenase products of arachidonate, such as TxA₂ and PGI₂.     

Effect of hemorrhagic shock on endotoxin-induced pulmonary hypertension and increased vascular permeability in unanesthetized sheep

The lung is very susceptible to sepsis or endotoxin injury in the trauma patient. We studied the effect of an episode of hemorrhagic shock and resuscitation on the prostaglandin-induced pulmonary hypertension and leukocyte-induced increased permeability phase of endotoxin lung injury. Eight unanesthetized sheep with chronic lung lymph fistula were bled 50% of blood volume for 2 hr, then resuscitated. Thromboxane, TxA2, levels increased from 0.1 to 0.6 ng/ml during shock, while blood white cell count decreased. Both parameters returned to baseline while lung lymph flow increased twofold during resuscitation with lymph being protein-poor, indicating no increase in permeability. Lung water was not increased but some pulmonary leukostasis was evident histologically after resuscitation. We then studied the effect of this process on all immediate endotoxin insult. Seven unanesthetized sheep were given 0.7 microgram/kg E. coli endotoxin alone, and again after shock and resuscitation, in paired studies performed 3 days apart. There was no difference in either the early pulmonary hypertension or the later increased permeability phase of endotoxin lung injury when comparing the paired studies, as measured by lymph flow and protein flux. Hemorrhagic shock, despite producing a transient increase in thromboxane and pulmonary leukocyte sequestration, does not accentuate the lung injury of endotoxin if the shock state is adequately resuscitated.     

Mechanisms of late hemodynamic and airway dynamic responses to endotoxin in awake sheep

The mechanism of sustained alterations in pulmonary hemodynamics and lung mechanics after endotoxin infusion in sheep remains unclear. We examined the effects of metaproterenol, propranolol, atropine, and ibuprofen on pulmonary artery pressure (Ppa), dynamic compliance (Cdyn), resistance to airflow across the lungs (RL), specific airway conductance (SGaw), and alveolar-arterial oxygen difference (delta AaPO2) (room air) given 2.5 h after endotoxemia (except for propranolol, which was given 1 h after metaproterenol) in awake sheep. Atropine infusion had no effect on any of the variables measured. Ibuprofen infusion immediately reduced mean Ppa from 31 +/- 2 (mean +/- SEM) to 24 +/- 2 cm H2O (p less than 0.05). Metaproterenol and ibuprofen immediately increased Cdyn and SGaw and decreased RL to near baseline (p less than 0.05). No intervention affected delta AaPO2 (p greater than 0.05). In sheep treated with metaproterenol, propranolol immediately returned lung mechanics (p less than 0.05) to premetaproterenol levels without affecting delta AaPO2 (p greater than 0.05). Ibuprofen reduced lung lymph thromboxane-B2 towards baseline levels (p less than 0.05). We conclude that endotoxemia causes prolonged bronchoconstriction and pulmonary hypertension in sheep, which is largely mediated by constrictor prostanoids rather than by cholinergic mechanisms and is reversible with ibuprofen given 2.5 h after endotoxin.     

Reduction of total hemolytic complement activity with Naja haje cobra venom factor does not prevent endotoxin-induced lung injury in sheep

We studied the effects of reducing total hemolytic complement activity with Naja haje cobra venom factor on the lung injury caused by intravenously infused endotoxin in 5 unanesthetized sheep with lung lymph fistulas. In normal sheep, infusions of lipopolysaccharide W from Escherichia coli (1.0 micrograms/kg) intravenously over 30 min caused increases in protein-rich lung lymph flow as well as the appearance in plasma and lung lymph of complement (C5)-derived chemotactic activity for polymorphonuclear leukocytes. Reduction of total hemolytic complement activity by treatment with Naja haje cobra venom factor (12 to 17 U/kg intraperitoneally) did not prevent the lung injury caused by endotoxin and also did not prevent the appearance in plasma and lung lymph of chemotactic activity. We conclude that although complement appears to be activated following intravenously infused endotoxin in sheep, a completely intact complement system is not necessary for endotoxin-induced lung injury.     

Failure of a protease inhibitor to affect the cardiopulmonary response to endotoxin when combined with a cyclooxygenase inhibitor

The administration of endotoxin produces an early increase in hydrostatic pressure and pulmonary lymph flow, which is associated with elevated levels of thromboxane A2 in the lymph and can be blocked by the cyclooxygenase inhibitor ibuprofen. Two hours after the administration of endotoxin a secondary response is seen. The pulmonary lymph flow is elevated in association with a change in microvascular permeability to protein, this phase of the response can be reduced by the administration of the proteolytic enzyme inhibitor gabexate mesilate. In the present study we administered both compounds to eight sheep prepared for chronic cardiopulmonary and lung lymph studies to reduce both phases with the drug combination. The phase I response was reduced but the changes in lung lymph flow, associated with the phase II response, were unaffected by treatment. It is concluded that the effect of gabexate mesilate on the secondary response to endotoxin must in some way be related to the release of prostanoids.     

Effect of catalase on endotoxin-induced acute lung injury in unanesthetized sheep

Administration of endotoxin intravenously to unanesthetized sheep causes an acute lung injury characterized by increased microvascular barrier permeability and subsequent pulmonary edema. Endotoxin-induced sheep lung injury can be attenuated by leukocyte depletion, and may be mediated by toxic metabolites of oxygen. We studied effects of administering catalase, which catalyzes conversion of hydrogen peroxide to oxygen and water, to sheep subsequently infused with endotoxin to test the hypothesis that hydrogen peroxide plays a role in the pathogenesis of lung injury. We found that infusions of endotoxin (1 microgram/kg) into untreated sheep caused the expected biphasic response, a transient, early, marked pulmonary arterial hypertension followed by a prolonged increase in protein-rich lung lymph flow characteristic of increased microvascular permeability filtration in the lungs. Intraperitoneal injections of catalase (50 mg/kg) prior to infusing endotoxin in these same sheep resulted in substantial catalase activity in plasma and in lung lymph, and attenuated the expected changes in pulmonary arterial pressure, lung lymph flow, and arterial leukocyte counts and oxygen tension after endotoxin infusions. Furthermore, mechanical elevation of hydrostatic pressure in the lungs of a catalase-treated sheep infused with endotoxin resulted in increased lung lymph flow with a decreased protein concentration, indicating that the microvascular barrier to fluid and protein was functionally intact. Administration of catalase that was inactivated by reaction with hydrogen peroxide in the presence of aminotriazole or administration of the catalase vehicle, thymol, had no effects on the sheep responses to endotoxin. We conclude that hydrogen peroxide plays a role in the pathogenesis of endotoxin-induced acute lung injury in sheep.     

The role of leukotriene B4 in endotoxin-induced lung injury in unanesthetized sheep

In order to examine the role of LTB4, a potent neutrophil chemokinetic and chemotactic factor, in the lung injury induced by Escherichia coli endotoxin, we measured LTB4 in systemic arterial blood plasma and lung lymph in unanesthetized sheep with chronic lung lymph fistulas. E. coli endotoxin (1 microgram/kg) infusion produced a biphasic response. The early period (Phase 1) was a transient pulmonary hypertension. The late period (Phase 2) was a more prolonged period characterized by an increase flow of lung lymph with a high concentration of protein, suggesting increased pulmonary vascular permeability. Peripheral leukocyte counts rapidly decreased during Phase 1 and leukopenia persisted for approximately 5 h. The concentration of LTB4 in arterial plasma and lung lymph significantly increased during Phase 1, and then decreased with a rebound significant increase during Phase 2. That is, LTB4 in plasma and lung lymph showed a biphasic increase after endotoxin infusion. Our data suggest that the elevation of LTB4 is related to the pulmonary leukocyte sequestration in the lung and may contribute to the lung vascular injury induced by endotoxin in unanesthetized sheep.     

Dose- and time-dependent changes in plasma catecholamines in response to endotoxin in conscious rats

Time- and dose-dependent changes in plasma catecholamines, heart rate, and blood pressure were studied in response to sublethal doses of intravenous (i.v.) bacterial endotoxin in conscious male rats. Hypotension occurred with high endotoxin (1,000 micrograms/kg), whereas hypertension occurred in the low-dose group (10 micrograms/kg). All groups had significant tachycardia, which was dose and time dependent, but heart rate was unchanged for the first 2 hr in the low-dose groups (100 and 10 micrograms/kg). Plasma levels of norepinephrine (NE) and epinephrine (E) increased with both dose and time and there was significant interaction of dose and time effects. NE levels increased maximally at 0.5 hr following the highest dose of endotoxin and remained elevated during the protocol. Plasma E levels were maximal at 0.5 hr in the high-dose group, but then declined while remaining significantly higher than the 10 and 100 micrograms/kg endotoxin-treated groups for the duration of the protocol. Peak E levels in the 100 and 10 micrograms/kg group occurred at 3.0 hr and then decreased at the 6.0 hr time. Significant increases in plasma catecholamines and heart rate with endotoxin in the absence of significant hypotension present the possibility that factors other than blood pressure may be mediating efferent sympathetic outflow in endotoxicosis.     

Effects of continuous infusion of nitroglycerin on pulmonary hemodynamics,lung lymph balance,and prostanoid products in the response to endotoxin in awake sheep

We examined the effects of continuous intravenous infusion of nitroglycerin (NTG) on lung dysfunction induced by endotoxemia in awake sheep chronically instrumented with lung lymph fistula. We measured the responses of hemodynamics, lung lymph balance, and thromboxane (Tx)B₂ and 6-keto-prostaglandin (PG) Fla levels in plasma and lung lymph to endotoxin administration (1 µg/kg, intravenously [IV], over 30 min) with and without continuous infusion of NTG (1 µg/kg/min). Continuous infusion of NTG alone (n = 5) over 5 hr did not significantly alter systemic, pulmonary hemodynamics, and/or lung lymph fluid filtration. Infusion of endotoxin alone (n = 7) caused remarkable increases in pulmonary artery pressure (Ppa) and lung lymph flow (Qlym) in the early phase. Continuous infusion of NTG (n = 6) significantly prevented the early increases in Ppa and Qlym after endotoxin. The increased values of TxB₂ and 6-keto-PGF₁ in both plasma and lung lymph after endotoxemia showed the same increases in groups with and without NTG. These findings suggest that the reduction of pulmonary artery pressure induced by NTG decreased the filtration of fluid into the lungs associated with endotoxemia in sheep, and that the mechanism of vasodilating action of NTG is not due to modifications of constrictive-dilated cyclo-oxygenase products of arachidonate, such as TxA₂ and PGI₂. Offprint requests to: K. Kubo     

Studies of an antiendotoxin antibody in preventing the physiologic changes of endotoxemia in awake sheep

In sheep, endotoxin (LPS) causes pulmonary hypertension, hypoxemia, leukopenia, exudation of protein-rich lung lymph, reduced dynamic compliance (Cdyn), and increased resistance to airflow (RL), changes similar to those seen in human sepsis and sepsis-induced ARDS. We used well-described methods in the awake sheep-endotoxin model to evaluate the effectiveness of a commercially manufactured antibody to prevent the physiologic changes of endotoxemia. In awake sheep with chronic lung lymph fistulas, we used a whole-body plethysmograph to measure Cdyn, RL, and FRC. Pulmonary artery, left atrial, and systemic arterial pressures were recorded continuously. Arterial blood gases (for calculating AaPO2), leukocyte counts, and lymph samples were collected every 30 min. Animals received a 30-min (2 mg/kg) infusion of antiendotoxin antibody 4 h before LPS (0.75 micrograms/kg) challenge (n = 4), or were given a mixture of LPS (0.75 micrograms/kg) and antibody (2 mg/kg) that had been incubated in vitro at 37 degrees C for 30 min before infusion (n = 6). A control group given only 2 mg/kg of antibody (n = 4) showed no change in any measured parameter, whereas control animals receiving LPS alone (n = 6) exhibited a typical endotoxin response. In all animals receiving endotoxin, Cdyn declined by approximately 50% within 30 to 60 min, and RL increased approximately sixfold over a similar time course. Accompanying the abnormalities in lung mechanics were pulmonary hypertension, leukopenia, and widening of the AaPO2.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of recombinant human tumor necrosis factor alpha, lymphotoxin, and Escherichia coli lipopolysaccharide on hemodynamics, lung microvascular permeability, and eicosanoid synthesis in anesthetized sheep

We infused recombinant human tumor necrosis factor alpha (rhTNF alpha), lymphotoxin (rhLT), and Escherichia coli 0111:B4 lipopolysaccharide (LPS) into anesthetized sheep with a lung lymph fistula to compare their effects on systemic and pulmonary hemodynamics, lung lymph dynamics, and eicosanoid release. rhTNF alpha (25-150 micrograms/kg, n = 6 sheep), but not rhLT (25 micrograms/kg, n = 3), rapidly increased lung lymph and plasma levels of 6-keto-prostaglandin F1 alpha (6-k-PGF1 alpha) and caused profound systemic vasodilation and hypotension. Meclofenamate pretreatment (10 mg/kg) of three other sheep given 25 micrograms/kg rhTNF alpha prevented the increase of lymph and plasma 6-k-PGF1 alpha levels, systemic vasodilation, and the early (less than 2 hrs) but not the late (4-6 hours) hypotension caused by rhTNF alpha. LPS (1 micrograms/kg, n = 11) induced a briefer increase of lymph 6-k-PGF1 alpha levels than did rhTNF alpha while plasma 6-k-PGF1 alpha levels did not increase. LPS induced more gradual hypotension than did rhTNF alpha but did not cause systemic vasodilation. LPS and rhTNF alpha, but not rhLT, increased lymph thromboxane B2 (TXB2) levels during the first hour of study, whereas only LPS acutely increased plasma TXB2 levels. LPS caused acute pulmonary vasoconstriction and greater acute pulmonary artery hypertension than did either rhTNF alpha or rhLT. Whereas LPS-treated sheep required less fluid transfusion than rhTNF alpha-treated sheep to maintain mean systemic arterial pressure greater than 50 mm Hg, LPS infusion caused a greater increase of lung lymph protein clearance. rhTNF alpha caused minimal alterations of lung microvascular permeability. We conclude that eicosanoid mediators contribute importantly to differences of systemic and pulmonary hemodynamics caused by these agents in sheep. rhTNF alpha cannot account for all of the LPS-induced hemodynamic, lung lymph, and eicosanoid responses in sheep.     

Hypoxanthine in lethal canine endotoxin shock.

Endotoxin shock was induced in Labrador retriever dogs by intravenous infusion of a lethal dose of Escherichia coli endotoxin (2 mg/kg body weight) over a three-hour period in order to study plasma hypoxanthine concentrations. The animals succumbed within 14 hours after start of the infusion. Terminally when aortic blood pressure dropped below 30 mm Hg and bradycardia had developed, the animals were resuscitated by external cardiac massage, artificial ventilation, and volume therapy. During shock no significant alteration of plasma hypoxanthine concentrations occurred. During the 12-minute period of resuscitation, however, hypoxanthine concentrations of both arterial and venous plasma increased rapidly compared to the initial values. The changes of the hypoxanthine concentration revealed an exponential pattern. The likely explanation for this phenomenon is is that during shock bypoxanthine was accumlated in the tissues due to tissue hypoxia and that the metabolite was washed out into the circulation during resuscitation.