Lung Lymph Protein Clearance Research Articles

Activated pulmonary intravascular macrophages increase pulmonary microvascular permeability in sheep

Pulmonary intravascular macrophages (PIMs) reside in the alveolar capillaries of sheep lung. However, the role of PIMs activation in the mechanism of increasing pulmonary microvascular permeability is not clear. We determined, using awake sheep with chronic lung lymph fistulas, the effects of intraarterial infusion of latex beads emulsion (1 microns in diameter) on lung lymph-dynamics. Sheep were divided into 3 groups; control, low dose latex and high dose latex groups. In control group, their lymph-dynamics were stable during the experimental period. In low dose latex group (5.46 x 10(9) beads/kg), lung lymph flow increased during the infusion period, but lung lymph protein clearance did not change. In high dose latex group (5.46 x 10(10) beads/kg), lung lymph flow began to increase during the infusion period and remained high, and lung lymph protein clearance increased significantly during and after the infusion of latex beads emulsion. The latex beads mainly distributed to lungs, and 70% of the beads were caught by PIMs in their phagosomes. These findings suggest that the activation of PIMs through their phagocytic uptake of circulating microparticles increases pulmonary microvascular permeability.

Role of neutrophils in lung injury after intestinal ischemia and reperfusion in dogs

We studied the role of neutrophils in lung injury after intestinal ischemia and reperfusion (I/R) in anesthetized dogs with lung lymph fistulae. One group was subjected to 2.5 hours of balloon occlusion of the superior mesenteric artery without laparotomy, followed by 3 hours of reperfusion (I/R group, n = 7). The other group was subjected to the same procedures, except for intestinal I/R (sham operation group, n = 6). In the sham operation group, lung fluid balance, hemodynamics, extravascular water volume (Qw 1: ml/g BFDW), myeloperoxidase activity in the lung (MPO: unit/g DW), H2O2 production by neutrophils in blood (mean DCF/cell), and migration of neutrophils into the lung lymphatic system did not significantly change. In the I/R group, both lung lymph flow (Jv) and protein clearance (Qp) increased more than 2.5 fold as compared with the baseline values, while capillary pressure (Ppc) and the ratio of lymph to plasma protein concentration (CL/Cp) remained almost the same as the baseline values. Qw1 also moderately increased. MPO activity, H2O2 production, and migration of neutrophils into the lung lymphatic system increased after I/R, and were more remarkable than in the sham operation group. These results suggest that activation and migration of primed neutrophils contributes to lung injury after intestinal ischemia and reperfusion.

Effects of High-Frequency Oscillatory Ventilation on Oleic Acid-Induced Lung Injury in Sheep

High-frequency oscillatory ventilation (HFOV) is a possible mechanical method for open lung strategies. The aim of this study was to examine whether HFOV has a beneficial effect on oleic acid-induced lung injury, with emphasis on changes in extravascular lung water. Thirteen anesthetized sheep prepared with a lung lymph fistula and vascular catheters for monitoring were randomly allocated to two experimental groups. In experiment 1, sheep (n = 6) were ventilated using conventional mechanical ventilation [CMV; 10 ml/kg of tidal volume, 70% oxygen, and positive end-expiratory pressure (PEEP) of 6 cmH(2)O after oleic acid administration (0.08 ml/kg)]. In experiment 2, sheep (n=7) were ventilated using HFOV (frequency=15 Hz, stroke volume=120 ml, mean airway pressure=15 cmH(2)O) after administration of the same dose of oleic acid as in experiment 1. Observation was continued for 4 h after oleic acid administration, then bronchoalveolar lavage (BAL) was performed and the lung wet-to-dry weight ratio was determined. Compared with CMV, HFOV significantly improved the deteriorated oxygenation during the late phase (2-4 h) of oleic acid-induced lung injury without any deterioration effects on pulmonary or systemic hemodynamics. HFOV showed significantly reduced lung lymph protein clearance, which paralleled significant decreases in wet-to-dry ratios and neutrophil counts in BAL fluid in the HFOV group. These findings suggest that HFOV could contribute to decreased lung lymph filtration in pulmonary microcirculation and improved oxygenation following oleic acid-induced lung injury in sheep.

INFLUENCE OF FRUCTOSE-1, 6-DIPHOSPHATE ON ENDOTOXIN-INDUCED LUNG INJURIES IN SHEEP.

Introduction Fructose-1, 6-diphosphate (FDP) is reported to have a salutary effect in endotoxin shock and sepsis. This investigation describes the effect of FDP on pulmonary and systemic hemodynamics, lung lymph protein clearance, and leukocyte count in sheep infused with E. coli endotoxin. Materials and Methods Anesthetized sheep (n = 18), some of which underwent thoracotomy to cannulate lymphatic nodes, were used in this study. Following stabilization, all sheep received E. coli endotoxin 5 μg/kg IV infusion over 30 minutes. Concomitant with the endotoxin infusion, half of the animals were randomly selected to receive an IV bolus of FDP (10%) 50 mg/kg followed by a continuous infusion of 5 mg/kg/min for 4 hours; the rest were treated in the same manner with glucose 10% in 0.9% NaCl. Results Pulmonary artery pressure (PAP) and resistance in the glucose group increased from 20.8 ± 1.6 to 36.7 ± 3.2 mm Hg (p Conclusion FDP treatment attenuated significantly the characteristic pulmonary hypertension, lung lymph protein clearance, and pulmonary vascular leakage seen in sheep infused with endotoxin.

Influence of Fructose-1,6-Diphosphate on Endotoxin-Induced Lung Injuries in Sheep

Fructose-1,6-diphosphate (FDP) is reported to have a salutary effect in endotoxin shock and sepsis. This investigation describes the effect of FDP on pulmonary and systemic hemodynamics, lung lymph protein clearance, and leukocyte count in sheep infused with Escherichia coli endotoxin. Anesthetized sheep (n = 18), some of which underwent thoracotomy to cannulate lymphatic nodes, were used in this study. After stabilization, all sheep received E. coli endotoxin, 5 microg/kg i.v. infusion over 30 min. Concomitant with the endotoxin infusion, half of the animals were randomly selected to receive an i.v. bolus of FDP (10%), 50 mg/kg, followed by a continuous infusion of 5 mg.kg(-1).min(-1) for 4 h; the rest were treated in the same manner with glucose (10%) in 0.9% NaCl. Pulmonary artery pressure (PAP) and resistance in the glucose group increased from 20.8 +/- 1.6 to 36.7 +/- 3.2 mmHg (P < 0.007) and from 531 +/- 114 to 1137 +/- 80 dyn.s(-1).cm(-5), respectively (P < 0.005). Despite an increase during endotoxin infusion, these parameters in the FDP group returned to control values. There were no differences in left ventricular pressures, cardiac output, heart rate, and arterial oxygen tension between the groups. In the glucose group, lymph protein clearance was higher (P < 0.01) and blood leukocyte count was lower (P < 0.02). The wet/dry lung weight ratio (g/g) for the glucose group was 5.57 +/- 0.04 and for the FDP-treated group 4.76 +/- 0.06 (P < 0.0005). FDP treatment attenuated significantly the characteristic pulmonary hypertension, lung lymph protein clearance, and pulmonary vascular leakage seen in sheep infused with endotoxin.

Methylene blue reduces lung fluid filtration during the early phase of endotoxemia in awake sheep.

To determine whether methylene blue (MB), an inhibitor of soluble guanylate cyclase and nitric oxide synthase, alters lung hemodynamics and fluid filtration after endotoxin in sheep. Prospective, randomized, controlled experimental study with repeated measurements. University animal laboratory. Eight yearling, awake sheep. Sheep were instrumented for a chronic study with vascular and lung lymph catheters. In two experiments, separated by 1 wk of recovery, the animals received intravenously either an injection of MB 10 mg/kg or a corresponding volume of 0.9% sodium chloride as pretreatment. Thirty minutes later, sheep received a bolus injection of Escherichia coli endotoxin 1 microg/kg, followed by either an infusion of MB 2.5 mg/kg/hr or a corresponding volume of 0.9% sodium chloride for 5 hrs. MB decreased the early phase endotoxin-induced rises in pulmonary capillary pressure and pulmonary vascular resistance. MB also reduced the increments in lung lymph flow (QL) and protein clearance (CL) as well as the rightward shift of the permeability-surface area product (PS). In addition, MB diminished the decrease in cardiac output, stabilized mean arterial pressure, and precluded the rise in plasma and lung lymph cyclic guanosine 3'-5' monophosphate. However, during the late phase, MB-treated sheep presented with a faster rise in QL with no difference in CL and PS from the endotoxemic controls. During the early phase of endotoxemia in sheep, MB attenuates lung injury by decreasing the enhanced lung fluid filtration as a result of reduced pulmonary capillary pressure and permeability. However, MB does not counteract the late phase increase in lung fluid filtration.

Effect of aminoguanidine on lung fluid filtration after endotoxin in awake sheep.

It has been suggested that enhanced generation of nitric oxide by inducible nitric oxide synthase (iNOS) may contribute to acute lung injury. We hypothesized that aminoguanidine (AG), a proposed selective inhibitor of iNOS, would alter pulmonary hemodynamics, fluid filtration, and gas exchange after endotoxin in chronically instrumented awake sheep. Eighteen sheep were randomly assigned to receive either AG (10 mg/kg + 1 mg/kg/h), or NaCl 0.9% intravenously for 4 h, beginning 2 h after injection of Escherichia coli endotoxin (1 microgram/kg). After endotoxin, pulmonary artery pressure (Ppa), capillary pressure (Pc), and vascular resistance index (PVRI) rose concomitantly with six-fold increments in lung lymph flow (Q L) and protein clearance (CL). Extravascular lung water (EVLW) doubled, as assessed with the thermal dye dilution technique; Pa(O(2)) decreased, AaPO(2) and venous admixture (Q S/Q T) increased. After AG, Q L and CL increased further by approximately 30%, whereas EVLW remained unchanged, despite an additional increase in Pc. Ppa, PVRI, and systemic vascular resistance index rose, whereas cardiac index and pulmonary blood volume index declined. In addition, Pa(O(2)) rose, and AaPO(2) and Q S/Q T decreased. We conclude that in endotoxemic sheep, AG improves gas exchange and increases Q L and CL, whereas EVLW remains unchanged in spite of enhanced Pc. Apparently, increased lymphatic drainage prevents EVLW from rising after AG.

Intravascular macrophage depletion attenuates endotoxin lung injury in anesthetized sheep.

We recently showed that we can selectively and safely deplete most (average 85%) of the pulmonary intravascular macrophages in sheep by intravenously infusing liposomes containing dichloromethylene bisphosphonate. After a 1-h stable baseline, we made a 6-h comparison after a 30-min intravenous endotoxin infusion (1 microg/kg) between six anesthetized control lambs and six anesthetized lambs in which the intravascular macrophages had been depleted 24 h previously. Three of the control lambs had been macrophage depleted and allowed to recover their intravascular macrophage population for >/=2 wk. After depletion, both the early and late pulmonary arterial pressure rises were dramatically attenuated. Our main interest, however, was in the acute lung microvascular injury response. The early and late rises in lung lymph flow and the increase in lung lymph protein clearance (lymph flow x lymph-to-plasma protein concentration ratio) were >90% attenuated. We conclude the pulmonary intravascular macrophages are responsible for most of the endotoxin-induced pulmonary hypertension and increased lung microvascular leakiness in sheep, although the unavoidable injury of other intravascular macrophages by the depletion regime may also contribute something.

Neutrophil recruitment as a factor limiting injury or promoting recovery from acute lung injury.

We studied 1) neutrophil mobilization in sheep given endotoxin (10 ng.kg-1.min-1, n = 5) for 4 h, 2) surviving (n = 17) and nonsurviving sheep (n = 8) during a 12-h infusion of endotoxin, and 3) adult sheep (n = 8) or lambs (n = 8) infused with endotoxin for 12 h. Bone marrow cells of sheep declined from a baseline value of 10,533 +/- 1,784 to 5,966 +/- 1,980 cells/microliter (P < 0.05) 4 h after endotoxin. After 12 h of endotoxin infusion, circulating neutrophils remained reduced from baseline values of 2,000-4,000 cells/microliter to 343 +/- 70 in lambs and 484 +/- 236 in nonsurviving sheep, while beginning to recover in surviving sheep to 1,838 +/- 467 cells/microliter. In lambs and nonsurviving sheep, a 12-h infusion of endotoxin increased lung lymph protein clearance tenfold compared with a fivefold increase in surviving sheep. Neutrophils cultured from sheep bone marrow exposed to lamb postendotoxin plasma failed to increase in cell number (609 +/- 229 to 610 +/- 182 cells/microliter), whereas similar cells exposed to adult sheep postendotoxic plasma showed a significant increase in cell number (1,069 +/- 101 to 2,293 +/- 448 cells/microliter, P < 0.05). Our results are consistent with the hypothesis that the ability to recruit neutrophils to the circulation during periods of inflammation is important in limiting the severity of acute lung injury.

Neutrophil adhesion blockade with NPC 15669 decreases pulmonary injury after total cardiopulmonary bypass

Background: Total cardiopulmonary bypass, in an ovine model, is associated with increased pulmonary thromboxane A 2 production, cellular sequestration of white cells and platelets, transient pulmonary hypertention, and increased lung lymph flow and lymph protein clearance when compared with respective findings with partial cardiopulmonary bypass. This study evaluates the effect of neutrophil adhesion blockade on lung injury after cardiopulmonary bypass. Methods: Two groups of anesthetized sheep were placed on total cardiopulmonary bypass without assisted ventilation. One group of seven sheep was treated before and during total cardiopulmonary bypass with the neutrophil adhesion blocker NPC 15669. A second group of seven sheep did not receive NPC 15669 treatment before total cardiopulmonary bypass. A third group of seven sheep was treated with NPC 15669 before initiation of partial cardiopulmonary bypass with continued assisted ventilation. Aortic occlusion and hypothermia were not used. After 90 minutes all sheep were separated from cardiopulmonary bypass, with resumption of assisted ventilation and pulmonary arterial flow. After 30 minutes the left atrial pressure was elevated mechanically. Hemodynamics, thromboxane A 2 levels, platelet levels, and white blood cell and plasma protein concentrations were measured before cardiopulmonary bypass and afterwards at four 15-minute intervals. Samples were taken from the right and left atria simultaneously. Lung lymph protein levels and flow were measured before and after cardiopulmonary bypass at two 30-minute intervals. Results: In the total cardiopulmonary bypass group not treated with NPC 15669 signs of lung injury developed after cardiopulmonary bypass. Animals treated with NPC 15669 did not manifest a similar degree of lung injury after either partial or total cardiopulmonary bypass. Increased pulmonary vascular resistance did not develop in treated sheep nor did sequestration of platelets or white blood cells occur. Despite the drug, increased pulmonary capillary permeability after total cardiopulmonary bypass persisted, but was reduced. Conclusions: Compared with unmodified total cardiopulmonary bypass, blockade of neutrophil adhesion with NPC 15669 reduces, but does not entirely eliminate, lung derangement after total cardiopulmonary bypass. (J T HORAC C ARDIOVASC S URG 1996;111:460-8)

Secretory leukoprotease inhibitor attenuates lung injury induced by continuous air embolization into sheep

Continuous air embolization (CAE) into the pulmonary arterial circulation of sheep results in functional and structural changes of chronic pulmonary hypertension. Release of elastin peptides into lung lymph during CAE and attenuation of CAE-induced pulmonary hypertension by neutrophil depletion suggest that neutrophil elastase may contribute to these changes. To investigate this notion, we treated awake sheep with a potent neutrophil elastase inhibitor, recombinant secretory leukoprotease inhibitor (SLPI) (100 mg/day by aerosol), during 12 days of CAE (CAE+SLPI; n = 7). Controls included sheep receiving CAE + vehicle (VEH) (n = 6), VEH alone (n = 3), and SLPI alone (n = 3). SLPI significantly attenuated the CAE-induced increases in lung lymph flow (day 8; 2.3 +/- 0.5 vs. 5.6 +/- 1.7 ml/15 min), protein clearance (day 8; 1.36 +/- 0.32 vs. 3.08 +/- 0.84 ml/15 min), and elastin peptide concentration (day 8; 243 +/- 41 vs. 398 +/- 44 ng/ml). SLPI delayed the onset of sustained pulmonary hypertension from day 8 to day 12. Both CAE groups showed similar structural changes in the pulmonary arteries. SLPI was well tolerated in control sheep and did not affect hemodynamics or structure. We conclude that serine proteases may contribute to the early initiation of chronic pulmonary hypertension but do not play a striking role in its eventual development.

Stimulation of pulmonary intravascular macrophages increases microvascular permeability in awake sheep.

The purpose of this study is to determine if stimulation of pulmonary intravascular macrophages (PIMs) increase microvascular permeability in sheep. We infused latex microbeads, 1 micron in diameter, for 1 hr continuously and analysed lung hemodynamic and lymph-dynamic changes. More than 70% of latex microbeads in the lung were assigned to PIMs, and caught in their phagosomes as determined by morphological examination. This implies that infused latex microbeads predominantly stimulate PIMs. Pulmonary arterial pressure increased during the infusion period, and returned to baseline after the infusion period. Lung lymph flow increased and remained high while the lymph to plasma protein ratio ultimately increased above baseline. This implies that infusion of latex microbeads increases pulmonary microvascular permeability. The increase in lung lymph protein clearance was blocked completely by pretreatment with indomethacin, but not with a thromboxane synthetase inhibitor (OKY-046). These data indicate that the increase in microvascular permeability is mediated by an arachidonic acid cyclooxygenase metabolites but not by thromboxane. We conclude that PIMs can act as an initiator to increase pulmonary microvascular permeability by releasing arachidonic acid cyclooxygenase metabolites through their stimulation with latex beads.

Downregulation of blood and bone marrow neutrophils decreases expression of acute lung injury in sheep.

We have shown that infusion of zymosan-activated plasma (ZAP) in sheep causes acute lung injury and downregulates peripheral blood neutrophils in that elicited superoxide release is reduced for at least 24 h after the infusion. The present study was designed to test the following hypotheses: 1) peripheral blood neutrophils are representative of neutrophils marginated in the pulmonary circulation, 2) blood neutrophils are downregulated because neutrophils developing in bone marrow are similarly affected, and 3) downregulated neutrophils have a reduced capacity to produce tissue injury. In a series of experiments in 21 sheep, we showed that elicited superoxide release was similar in peripheral blood neutrophils and in marginated neutrophils washed out of the pulmonary vascular bed. Measurements of superoxide release from blood and bone marrow neutrophils collected 2-24 h after ZAP infusion revealed progressive downregulation with time and greater downregulation of superoxide release in bone marrow neutrophils compared with peripheral blood neutrophils. Finally, after downregulating peripheral blood neutrophils, subsequent infusion of ZAP in conscious sheep produced sequestration of neutrophils in the pulmonary circulation but failed to produce a sustained increase in lung lymph protein clearance. The results suggest that neutrophil downregulation, as measured in vitro, is expressed in vivo as reduced ability of neutrophils to produce tissue injury when challenged by an activating agent.

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.

PGE1 inhibited PMN attachment to air emboli in vivo during infusion of ZAP without preventing lung injury.

Prostaglandin E1 (PGE1) treatment of neutrophils inhibits their adherence to substrates in vitro, including endothelial cell monolayers. Demonstration that PGE1 inhibits neutrophil adherence in vivo in the lung, however, is complicated by PGE1 effects on cells other than neutrophils, such as endothelial cells. To determine whether PGE1 inhibits neutrophil adherence properties in vivo, we used air emboli as intravascular targets for neutrophil attachment. Four experimental conditions were studied in anesthetized and awake sheep that were treated with 1) PGE1 and air emboli, 2) saline and air emboli, 3) PGE1 and zymosan-activated plasma (ZAP) + air emboli, and 4) saline and ZAP + air emboli. PGE1 (30 ng.kg-1.min-1) or saline was infused continuously 1 h before and 1 h during the infusion of air emboli (group 1; n = 13 sheep) or ZAP + air emboli (group 2; n = 13 sheep). The number of neutrophils (PMNs) attached to air emboli in four anesthetized sheep per condition was significantly less in sheep given PGE1 and ZAP + air emboli [8 +/- 3 (SD) PMNs/mm of embolus perimeter] than in the other three conditions (14-21 PMNs/mm; P less than 0.05). Repeated experiments in five awake sheep per group showed that PGE1 treatment did not prevent increased lung lymph protein clearance in either group compared with saline treatment. We conclude that PGE1 specifically inhibited attachment of ZAP-activated neutrophils to air emboli in vivo. The lack of pathophysiological protection suggests that PGE1-induced alterations in neutrophil attachment properties were independent of other cellular activation responses.

Attenuation of the pulmonary vascular response to endotoxin by a thromboxane synthesis inhibitor (UK-38485) in unanesthetized sheep

Previous studies have documented the phasic pulmonary vascular response to infused Eschericha coli endotoxin in unanesthetized sheep. Cyclooxygenase inhibition attenuates the initial vasoconstrictive phase (phase I) but not the late phase of increased microvascular permeability (phase II). We undertook to selectively inhibit thromboxane A 2 synthesis and assess the pulmonary microvascular response to endotoxin. Twelve paired studies were carried out in six sheep prepared with chronic lung lymph fistulas and pressure monitoring catheters. Each sheep received E. coli endotoxin (0.5 μg/kg) at time 0, both alone (control group) and 1 hr after pretreatment with a thromboxane synthetase inhibitor (UK-38485, 2 mg/kg). The animals were monitored for 1–2 hr prior to and 5 hr following endotoxin infusion to ensure a steady-state baseline and a complete late response. The pairs of studies were done in random order. In the presence of UK-38485, endotoxin caused significantly less pulmonary hypertension and shorter duration of leukopenia and lower lung lymph flow and lymph protein clearance rates than did endotoxin alone. The differences in lymph protein clearance were more pronounced in phase II. These data suggest that both the vasoconstrictive and permeability phases of the pulmonary vascular response to endotoxin may be modified on endogenous thromboxane A 2.

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.

In vivo biology of recombinant interleukin-2 infusion in sheep: cardiopulmonary manifestations of an intravascular immune-inflammatory response.

We have described the physiologic changes that occur in the conscious sheep during five days of dosing with rIL-2. Major effects noted were a decrease in systemic vascular resistance (vasodilation) accompanied by an increase in cardiac output (blood flow) and heart rate and a mild increase in pulmonary vascular resistance (vasoconstriction). Body temperature increased and may have contributed to the peripheral vasodilation. Lung microvascular fluid and protein flux increased following rIL-2 administration, as evidenced by an increase in lung lymph flow and protein clearance, and circulating levels of leukocytes decreased. These phenomena were temporally related. Since the composite biologic response that occurred following rIL-2 administration was characterized by changes in vascular caliber and blood flow, increased vascular permeability, and margination of leukocytes, we propose that the response be viewed as an intravascular inflammatory reaction.

Lung injury and neutrophil density during air embolization in sheep after leukocyte depletion with nitrogen mustard.

The hypothesis that neutrophils are a major mediator of acute lung injury is based in part on the results from leukocyte depletion studies in which peripheral leukopenia is induced by administration of chemotherapeutic agents or antileukocyte serum. Because of valid concerns about the specificity and multiplicity of effects these regimens have in vivo, we designed a correlative structure-function study of the impact of one depletion regimen on the intrapulmonary density of neutrophils in two groups of sheep. We gave one group of four awake sheep repeated injections of nitrogen mustard (0.4 mg/kg body weight on the ninth, sixth, and third day before the experiment) to lower circulating leukocyte counts to less than 1% of their normopenic value. The other group of four awake sheep was not treated before the experiment (normopenic sheep). On the day of the experiment, the sheep were anesthetized to measure hemodynamics and lung lymph dynamics, and to take lung tissue for morphologic examination before and during 4 h of continuous venous air embolization. Reduction of circulating leukocytes by greater than 99% of normopenic values only lowered pulmonary intravascular neutrophil density by about 80%. In baseline lung biopsies, neutrophil density in small pulmonary arteries (1 to 0.1 mm in diameter) in the nitrogen-mustard-treated sheep averaged 51 +/- 23 (+/- 1 SD) cells/mm2 of blood area versus 291 +/- 40 in the normopenic sheep. During venous air embolization, neutrophils sequestered in the pulmonary arterial microvessels of both groups (210 +/- 27 cells/mm2 of blood area in the nitrogen-mustard-treated sheep versus 1,217 +/- 49 in the normopenic sheep). Parallel increases in neutrophil density occurred in alveolar capillaries and small pulmonary veins. Neutrophils attached to the intravascular air emboli and to microvascular endothelial cells. Endothelial cell gaps were seen in about 30% (13 gaps in 48 microvessels) of the small arteries in the nitrogen mustard-treated sheep versus about 80% (38 gaps in 48 microvessels) in the normopenic sheep. Lung lymph protein clearance nearly doubled in the nitrogen mustard-treated sheep and tripled in the normopenic sheep during venous air embolization compared with the respective baseline clearance values. We suggest that methods used to deplete circulating leukocytes do not assure removal of neutrophils from the lungs; the remaining neutrophils appear capable of responding to intravascular inflammatory stimuli.

Corticosteroids prevent acute lung dysfunction caused by thoracic irradiation in unanesthetized sheep.

We sought to determine the effect of corticosteroid therapy in a new acute model of oxidant lung injury, thoracic irradiation in awake sheep. Sheep were irradiated with 1,500 rads to the whole chest except for blocking the heart and adjacent ventral lung. Seven experimental sheep were given methylprednisolone (1 g intravenously every 6 h for four doses) and thoracic irradiation; control sheep received only irradiation. In irradiated control sheep, lung lymph flow increased from baseline (7.6 ml/h) to peak at 3 h (13.2), and lung lymph protein clearance increased from 5.1 to 9.7 ml/h. Mean pulmonary artery pressure increased in the irradiated control sheep from 19 to 32.4 cm H2O, whereas the lung lymph thromboxane concentration increased from 0.09 to 6.51 ng/ml at 3 h. Arterial oxygen tension in irradiated control sheep fell gradually from 86 mm Hg at baseline to 65 mm Hg at 8 h. Methylprednisolone administration significantly prevented the increase in lung lymph protein clearance, mean pulmonary artery pressure, and lung lymph thromboxane concentration. Methylprednisolone also prevented the fall in arterial oxygen tension after thoracic irradiation, but did not prevent a further decrease in lymphocytes in blood or lung lymph after radiation. We conclude that corticosteroid therapy prevents most of the acute physiologic changes caused by thoracic irradiation in awake sheep.