Isolated Lung Preparation Research Articles

Alveolar sodium and liquid transport in mice.

We have developed a simple isolated lung preparation for measurement of liquid and solute fluxes across mouse alveolar epithelium. Liquid instilled into air spaces was absorbed at the rate (J(w)) of 3.7 +/- 0.32 ml x h(-1) x g dry lung wt(-1) x J(w) was significantly depressed by ouabain (P < 0.001) and amiloride (P < 0.001). Omission of glucose from the instillate or addition of the Na(+)-glucose cotransport inhibitor phloridzin did not affect J(w). However, the low epithelial lining fluid glucose concentration (one-third that of plasma), the larger-than-mannitol permeability of methyl-alpha-D-glucopyranoside, and the presence of Na(+)-glucose cotransporter SGLT1 mRNA in mouse lung tissue suggest that there is a Na(+)-glucose cotransporter in the mouse alveolar-airway barrier. Isoproterenol stimulated J(w) (6.5 +/- 0.45 ml x h(-1) x g dry lung wt(-1); P < 0.001), and this effect was blocked by amiloride, benzamil, ouabain, and the specific beta(2)-adrenergic antagonist ICI-118551 but not by atenolol. Similar stimulation was obtained with terbutaline (6.4 +/- 0.46 ml x h(-1) x g dry lung wt(-1)). Na(+) unidirectional fluxes out of air spaces varied in agreement with J(w) changes. Thus alveolar liquid absorption in mice follows Na(+) transport via the amiloride-sensitive pathway, with little contribution from Na(+)-glucose cotransport, and is stimulated by beta(2)-adrenergic agonists.

Protective effects of celsior in lung transplantation

Background: Celsior is a new preservation solution for heart transplants that recently has been shown also to improve protection of pulmonary grafts. As these data were obtained in isolated lung preparations, we sought to perform further tests with an in vivo model of allogeneic lung transplantation. Methods The left lungs of 41 rats were either transplanted immediately after harvest (controls) or flushed with and cold stored in Celsior or the blood-based Wallwork solution for 5 or 12 hours. Lungs were then reperfused for 30 minutes, after which ligation of the contralateral pulmonary artery and bronchus made the recipient rat exclusively dependent on the transplanted lung. Assessment of preservation was made on functional (blood gases, pulmonary hemodynamics) and structural (dry-to-weight ratio, light microscopy, myeloperoxidase [MPO] content) end points. Results The protective effects of Celsior were primarily manifest, once the contralateral lung had been functionally excluded, as a better preservation of oxygen tensions in the 5-hour storage experiments (416 ± 52 mm Hg vs 406 ± 59 mm Hg in controls [ p = NS] and vs 239 ± 34 mm Hg in Wallwork [ p < 0.05 vs the 2 other groups]) and a smaller increase in pulmonary vascular resistance in the 12-hour storage experiments (10.2 ± 4.1 mm Hg/mL/minute vs 3.2 ± 1.1 mm Hg/mL/minute in controls [ p = NS] and vs 23.1 ± 4.3 mm Hg/mL/minute in Wallwork [ p < 0.02 vs Celsior, p < 0.002 vs controls]). Survival was also longer in the 12-hour preserved Celsior group. Other end points were not significantly different between the two preservative solutions. Conclusion These data support the efficacy of Celsior as a flush-out and storage solution for pulmonary grafts. Given its previously documented ability to adequately preserve heart transplants, Celsior might provide a unified “solution” to thoracic organ preservation.

Fluorescein-labeled dextran concentration is increased in BAL fluid after ANTU-induced edema in rats.

Several methodologies have been developed to assess alveolocapillary membrane permeability in acute lung injury. The purpose of this study was to determine the reliability of FITC-dextran compared with radioactive tracers to assess lung permeability alterations. After intraperitoneal administration of alpha-naphthylthiourea (ANTU, 50 mg/kg) or DMSO-ANTU vehicle, the animals were euthanized and their lungs were studied in an isolated-lung preparation. FITC-dextran or radiolabeled tracers were added to the perfusate. At 2 h the bronchoalveolar lavage (BAL) fluid from the ANTU group showed a significantly greater amount of fluorescence in the supernatant after centrifugation of BAL fluid compared with the DMSO group. Consistent results were observed with the radioactive tracers: there was an increase in extravascular albumin space and extravascular lung water compared with the control group. No cleavage of the FITC from the dextran molecule was evident by chromatography comparing samples recovered from the BAL fluid to the pure FITC-dextran molecule. In conclusion, measurement of FITC-dextran in the supernatant of BAL fluid after intravascular administration is a reliable method of assessing lung permeability changes in vivo and ex vivo.

Increased Nitric Oxide in Exhaled Gas Is an Early Marker of Hypovolemic States

Acute hemorrhage is associated with a variety of physiologic and metabolic alterations, including vascular hyporeactivity and endothelial cell dysfunction. The lung is a major target organ during hemorrhagic shock. The effect of acute hemorrhage on NO production in the lung is not well described. In the present study we examined the effect of acute hemorrhage on exhaled NO (NOe), and studied how changes in blood volume and flow affect NOe. Anesthetized and mechanically ventilated rabbits were used. The effect of acute hemorrhage by slow exsanguination on NOe was examined using chemiluminescence. Because hemorrhagic shock is associated with decreased pulmonary blood flow, we established an isolated lung preparation perfused with autologous blood (Hct = 17.4%) and studied the effect of pulmonary flow rate on NOe independent of metabolic changes. In order to separate the effect of flow from the effect of changes in blood volume, we examined the effect of flow in isolated lungs perfused with a blood-free albumin solution (PAS). In the isolated lung, ventilation was similar to that used in the intact animal, and temperature, pH,pCO2, andPO2were kept normal. Prior to exsanguination, baseline NOe in the intact animal was 24 ± 3 ppb. At 5, 10, 15, and 20 min after initiating the hemorrhage, NOe rose to 31 ± 3, 51 ± 7, 94 ± 10, and 154 ± 16 ppb, respectively (P< 0.05). During baseline conditions in the blood-perfused isolated lungs (200 ml/min), NOe was 35 ± 3 ppb. When flow was decreased to 70 and 0 ml/min, NOe increased to 37 ± 3 and 56 ± 6 ppb, respectively (P< 0.001). During baseline conditions in the PAS-perfused lungs (70 ml/min), NOe was 94 ± 13 ppb and was unaffected by changes in flow. The perfusion pressure in the isolated lungs was in the normal range. Reduction in blood flow rate in the isolated lung was associated with less than twofold increase in NOe. This was attributed to reduction in red blood cell volume and not due to changes in blood flow rate. Reduction in flow in the intact animal during hemorrhage generated more than threefold increase in NOe, suggesting that neurohumoral mediators, in addition to changes in flow, play an important role in determining NOe in the intact condition. NOe began to rise immediately after exsanguination began, and therefore may be a useful early marker of acute hemorrhagic shock and hypovolemia. This information may be useful in the intensive care setting.

Quantitative analysis of transpleural flux in the isolated lung.

In this study, the loss of inert gas through the pleura of an isolated ventilated and perfused rabbit lung was assessed theoretically and experimentally. A mathematical model was used to represent an ideal homogeneous lung placed within a box with gas flow (Vbox) surrounding the lung. The alveoli are assumed to be ventilated with room air (VA) and perfused at constant flow (Q) containing inert gases (chi) with various perfusate-air partition coefficients (lambda p,x). The ratio of transpleural flux of gas (Vplx) to its total delivery to the lung via pulmonary artery (Vv), representing fractional losses across the pleura, can be shown to depend on four dimensionless ratios: 1) lambda p,x, 2) the ratio of alveolar ventilation to perfusion (VA/Q), 3) the ratio of the pleural diffusing capacity (Dplx) to the conductance of the alveolar ventilation (Dplx/VA beta g, where beta g is the capacitance coefficient of gas), and 4) the ratio of extrapleural (box) ventilation to alveolar ventilation (Vbox/VA). Experiments were performed in isolated perfused and ventilated rabbit lungs. The perfusate was a buffer solution containing six dissolved inert gases covering the entire 10(5)-fold range of lambda p,x used in the multiple inert gas elimination technique. Steady-state inert gas concentrations were measured in the pulmonary arterial perfusate, pulmonary venous effluent, exhaled gas, and box effluent gas. The experimental data could be described satisfactorily by the single-compartment model. It is concluded that a simple theoretical model is a useful tool for predicting transpleural flux from isolated lung preparations, with known ventilation and perfusion, for inert gases within a wide range of lambda.

Role of potassium channels and nitric oxide in the effects of iloprost and prostaglandin E1 on hypoxic vasoconstriction in the isolated perfused lung of the rat.

1. The aims of this study were to compare in the rat isolated perfused lung preparation, the antagonist effects of iloprost, a stable analogue of prostacyclin, and prostaglandin E1 (PGE1) on the hypoxic pulmonary pressure response, and to investigate the possible involvement of KATP and KCa channels and of EDRF (NO) in the effects. In addition, iloprost and PGE1 effects were compared to those of adenosine and forskolin. 2. Isolated lungs from male Wistar rats (260-320 g) were ventilated with 21% O2 + 5% CO2 + 74% N2 (normoxia) or 5% CO2 + 95% N2 (hypoxia) and perfused with a salt solution supplemented with ficoll. Glibenclamide (1 microM), charybdotoxin (0.1 microM), NG-nitro-L-arginine methyl ester (L-NAME, 100 microM) were used to block KATP, KCa channels and NO synthesis, respectively. 3. Iloprost, PGE1, adenosine and forskolin caused relaxation during the hypoxic pressure response. The order of potency was: iloprost > PGE1 = forskolin > adenosine. EC50 values were 1.91 +/- 0.52 10(-9) M, 3.31 +/- 0.58 10(-7) M, 3.24 +/- 0.78 10(-7) M and 7.70 +/- 1.68 10(-5) M, respectively. Glibenclamide, charybdotoxin and L-NAME inhibited partially the relaxant effects of iloprost and forskolin but not those of PGE1. 4. It is concluded that in the rat isolated lung preparation, iloprost and forskolin but not PGE1 dilate pulmonary vessels partly through KATP channels, KCa and nitric oxide release. Furthermore our results suggest that the role of cycli AMP in these effects is not unequivocal.

Increase of lung sodium-potassium-ATPase activity during recovery from high-permeability pulmonary edema.

Previous studies have suggested that recovery from pulmonary edema may be dependent on active sodium ion transport. Most of the data supporting this concept came from work done in isolated type II cells, isolated lung preparations, or in models of alveolar flooding. There is a limited amount of information regarding the role of active sodium ion transport in vivo. Furthermore, most of this information was obtained in one model of pulmonary edema, the hyperoxic lung injury model. The purpose of these experiments was then to measure the activity of the sodium-potassium-adenosinetriphosphatase (Na(+)-K(+)-ATPase), the active component of the sodium transport process and an indirect marker of active sodium transport, during recovery from thiourea-induced pulmonary edema in rats. Na(+)-K(+)-ATPase activity was significantly increased during recovery from lung edema. This increase could not be accounted for by the Na(+)-K(+)-ATPase activity present in inflammatory cells recruited in the lung by the injury process or by a direct impact of thiourea on the enzyme. Alveolar flooding, induced by instillation of a protein-containing solution into the airways of ventilated rats also increased the activity of Na(+)-K(+)-ATPase, suggesting that activation of the enzyme is probably secondary to either the presence of edema or the physiological consequences associated with edema. The quantity of lung Na(+)-K(+)-ATPase protein was also elevated during edema resolution, indicating that augmented synthesis of this enzyme underlies the increased enzyme activity observed. The quantity of Na(+)-K(+)-ATPase protein in alveolar type II cells was also significantly enhanced during recovery from edema, suggesting that these cells contribute to active sodium transport in vivo. The results of this study suggest that active sodium transport could participate in the resolution of pulmonary edema.

Salt and water transport across alveolar and distal airway epithelia in the adult lung.

Substantial progress has been made in understanding the role of the distal airway and alveolar epithelial barriers in regulating lung fluid balance. Molecular, cellular, and whole animal studies have demonstrated that reabsorption of fluid from the distal air spaces of the lung is driven by active sodium transport. Several different in vivo, in situ, and isolated lung preparations have been used to study the mechanisms that regulate fluid transport in the normal and injured lung. Catecholamine-dependent and -independent regulatory mechanisms have been identified that modulate fluid transport, probably by acting on apical sodium channel uptake or the activity of the Na, K-ATPase pumps. Recently, a family of molecular water channels (aquaporins) has been identified that are small (approximately 30 kDa) integral membrane proteins expressed widely in fluid-transporting epithelia and endothelia. At present, four different water channels have been identified in trachea and lung. Measurements of osmotic water permeability in in situ perfused lung and isolated perfused airways suggest a significant contribution of these molecular water channels to measured water permeability. However, further studies are required to determine the role of these water channels in normal pulmonary physiology and disease. Recent studies have provided new insights into the role of the alveolar epithelial barrier in clinical and experimental acute lung injury. Unlike the lung endothelium, the alveolar epithelium is resistant to several clinically relevant types of injury, including endotoxemia and bacteremia as well as aspiration of hyperosmolar solutions. In addition, even when the alveolar barrier has been injured, its capacity to transport edema fluid from the distal air spaces of the lung recovers rapidly. Future studies need to integrate new insights into the molecular mechanisms of alveolar epithelial sodium and water transport with functional studies in the normal and injured lung.

Pulmonary Pharmacology of DT-TX 30 SE, a Potent Selective Combined Thromboxane Synthetase Inhibitor and Receptor Antagonist, in Guinea Pigs

A novel chemical compound, DT-TX 30 SE (E-6-(4-(2-(4-chlorobenzenesulphonylamino)-ethyl)phenyl)-6-(3-pyridyl)-hex-5-enoic acid), was studied in various models of guinea pig pulmonary function. The compound was a potent inhibitor (ED50 0.019 mg/kg, i.v.) of bronchospasm induced by the thromboxane receptor agonist U-46619, indicating thromboxane receptor antagonism. At even lower doses (ED50 0.0036 mg/kg, i.v.), it blocked arachidonic acid-induced bronchospasm. Interpretation of the latter results as evidence for additional thromboxane synthetase inhibitory activity was supported by the inhibition of arachidonic acid- or bradykinin-induced thromboxane B2 production in an isolated lung preparation, although prostaglandin E2 and prostaglandin 6-oxo-F1α production measured at the same time were not inhibited. The potency of DT-TX 30 SE was compared with thromboxane receptor antagonists and synthetase inhibitors described in the literature. As a receptor antagonist, DT-TX 30 SE was significantly more potent than BM 13505 and BM 13177 (assessed by antagonism of U-46619-induced bronchospasm), but less potent than SQ 29548, while as a thromboxane synthetase inhibitor, it was significantly more potent than OKY 046 and UK 37248 as assessed by antagonism of arachidonic acid-induced bronchospasm or (OKY 046) inhibition of thromboxane production in isolated lung. The compound was active by the oral route as shown by its ability, at 10 mg/kg, p.o., to significantly reduce the immediate allergic response of sensitized guinea pigs to an ovalbumin aerosol.

Measurement of lung oxygen consumption in a patient after double-lung transplant

A 48-year woman underwent double-lung transplantation for treatment of severe emphysema. She required venous-arterial extracorporeal membrane oxygenation (ECMO; Bio-Medicus pump, model 540T; Bio-Medicus, Inc., Eden Prairie, Minn.; Medtronic/Carmeda Bioactive Surface with Maxima Hollow Fiber oxygenator CB 1380; ECMO flow rate 5 L/min, Medtronic, Inc., Minneapolis, Minn.) to correct severe nonpulsatile arterial pressure hypoxemia and cardiovascular instability. A postoperative 12:39 30.1 38 chest radiograph demonstrated bilateral alveolar infil12:40 18.3 27 trates compatible with acute lung injury. 12:41 15.2 30 On the second postoperative day, we measured oxygen 12:42 12.8 21.6 consumption (Vo2) and carbon dioxide excretion (Vco2) 12:43 11.2 22.7 by means of respiratory gas analysis with a metabolic cart 12:44" 7.7 19.6 (Deltatrac; SensorMedics Corp., Yorba Linda, Calif.). 12:45" 8.2 18.4 Blood flow through the pulmonary circulation was varied 12:46" 9.7 18.3 by adjusting the ECMO flow rates during the study 12:47" 6.9 19.6 interval. The patient was ventilated with a Puritan-Ben12:48" 5.1 15.7 nett 7200e ventilator (Puritan-Bennett Corp., Portable Ventilator Division, Boulder, Colo.) set on a tidal volume ECMO flow rate 2 L/rain, of 600 ml with a respiratory rate of 4 breaths/rain, positive cardiac output 3.43 L/min end-expiratory pressure of 10 cm H20, and inspired 13:43 46.5 77,6 oxygen fraction of 0.5. With the ECMO flow at 5 L/rain, 13:44 41.5 75,9 there was a nonpulsatile pulmonary arterial tracing with a 13:45 43.4 76.1 mean pressure of 8 mm Hg, which was inferred to reflect 13:46 47.7 75.5 no flow in the pulmonary artery. The simultaneous non13:47 53.6 78.0 pulsatile radial arterial tracing confirmed the absence of 13:48" 67.2 83.4 aortic valve opening. These settings were maintained for 13:49" 65.9 80.5 10 minutes, during which time the readings stabilized to 13:50" 68.4 80.0 yield, during a 5-minute period: Vo2, 7.8 -+ 1.7 ml/min 13:51" 70.1 81.2 (mean + standard deviation); and Vc% 18.3 -+ 1.6 ml/min 13:52" 72.1 79.8 (Table I). Respiratory quotient (RQ) was 1.97 + 0.05. When the ECMO flow rate was reduced gradually to 2 L/min, there was a return of pulmonary artery flow. This was evidenced by the reappearance of pulsatile pulmonary arterial and radial arterial tracings. Furthermore, a thermodilution cardiac output was measured at 3.43 L/rain. V% increased progressively and stabilized (after 5 rain-

A kinetic investigation of the pulmonary metabolism of dopamine in rats shows marked differences compared with noradrenaline

The aim of this study was to investigate the deamination of dopamine in the intact pulmonary circulation of isolated lungs of the rat. The first part of the study showed that dopamine is not converted to noradrenaline by dopamine-beta-hydroxylase (DBH) when dopamine is perfused through isolated lung preparations with monoamine oxidase (MAO) and catechol-O-methyltransferase (COMT) inhibited. Hence, it was not necessary to inhibit DBH in subsequent experiments. The metabolite profile for deamination of dopamine in the lungs was examined by determining whether MAO and semicarbazide-sensitive amine oxidases (SSAO) contribute to the deamination of dopamine (and noradrenaline), and by determining the activity of MAO (kMAO) for the metabolism of dopamine. Lungs were perfused with 1 nmol/l 3H-dopamine or 3H-noradrenaline with COMT inhibited and, in experiments to determine the contribution of SSAO to deamination, with MAO inhibited. Inhibition of MAO reduced the deamination of dopamine and noradrenaline by 99.8% and 98.6%, respectively, indicating that MAO, and not SSAO, was responsible for deamination of the catecholamines in the lungs. The kMAO value for deamination of dopamine was 3.89 min-1. Further experiments were carried out to determine the contributions of MAO-A and MAO-B to the deamination of dopamine in lungs perfused with 1 nmol/l 3H-dopamine and 100 nmol/l lazabemide or 300 nmol/l Ro41-1049, respectively.(ABSTRACT TRUNCATED AT 250 WORDS)

Contribution of pulmonary versus systemic perfusion of airway smooth muscle

Recent studies suggest a significant contribution of the pulmonary circulation to the perfusion of large airways. In this study we used anesthetized ventilated sheep (n = 19) to determine the functional contribution of the pulmonary circulation to airway smooth muscle. We performed sequential intravenous challenge with methacholine chloride (MCh; 0.25-2.5 mg/ml) to determine airway resistance (Raw) changes in the intact animal, after bronchial artery cannulation that essentially removed bronchial arterial delivery of MCh, and in an isolated lung preparation. After blocking the vagal reflex component of this response, we found that intravenous MCh in the intact preparation resulted in an average 2.2 +/- 0.5 cmH2O.l-1.s increase (181%) in Raw. After prevention of bronchial arterial delivery of MCh, Raw increased by 0.8 +/- 0.3 cmH2O.l-1.s (64%; P < 0.01 compared with intact preparation). In the isolated lung preparation, Raw increased by 0.6 +/- 0.2 cmH2O.l-1.s (63%; P < 0.01 compared with intact preparation). These results demonstrate that in sheep, the bronchial artery provides the major route for delivery of intravenously administered agonists to airway smooth muscle. Considering the large dilutional effect of an intravenously administered agonist by the time it reaches the bronchial artery, we conclude that the pulmonary component of agonist delivery to large airways is < 10% and unlikely to play a major physiological role.

Acute lung injury isolated to an in situ lung preparation causes sustained reflex cardiovascular depression in dogs.

We tested the hypothesis that acute lung injury (ALI) isolated to a perfused in situ left lung preparation results in sustained reflex cardiovascular depression. Phorbol myristate acetate (PMA), an agent that activates neutrophils, administered into the isolated lung preparation of chloralose-anesthetized dogs resulted in ALI, as assessed by wet-to-dry weight ratios and histopathology, and significant decreases in heart rate (43%), mean arterial pressure (27%), aortic blood flow (29%) and maximum rate of change in left ventricular pressure (30%). Significant reflex effects occurred by 20 min after PMA administration and were sustained for 40 min (n = 7). Hemodynamic variables recovered when the left lung was denervated 60 min after PMA administration. Indomethacin administered into the isolated circulation before PMA (n = 5) did not significantly influence the ALI or reflex effects. Systemic atropinization (n = 6) prevented only the bradycardia. Left lung denervation before ALI (n = 3) prevented all reflex effects. We conclude that PMA administration into an isolated in situ lung preparation results in ALI and sustained reflex cardiovascular depression that is most likely elicited by pulmonary C-fiber stimulation and mediated by withdrawal of sympathetic efferent nerve activity.

The isolated heart-lung preparation in the cat an in situ model to study the role of the lungs in the disposition of drugs

In the search for drugs with an extreme short time course of action, compunds should be developed that are rapidly distributed to and temporarily stored in well-perfused organs. Since the lungs receive the complete cardiac output and have the ability to temporarily store drugs, we have developed an in situ, isolated lung preparation in the cat to study the contribution of the lungs to the disposition of drugs. The cat's own heart perfuses the lung in situ with autologous blood. The circulation between the left ventricle and the right atrium is short-circuited via an aorta-caval shunt. The right forelimb is added to study pharmacodynamics simultaneously (only for muscle relaxants). Validation of the model for 180 min of perfusion showed complete isolation of the organs without major biochemical changes or edema and a stable muscle response. In pilot experiments with two structurally related muscle relaxants, initial muscle relaxation was followed by spontaneous recovery of neuromuscular function and a gradually decreasing plasma concentration, indicating partial disposition by the lungs. This was confirmed by direct concentration measurements in the lung. The present model may provide a powerful experimental tool to elucidate the role of the lungs in the disposition of drugs.

Is nitric oxide released in oleic acid lung injury?

Inhibitors of endothelium-derived nitric oxide synthesis or activity have been reported to enhance hypoxic vasoconstriction in isolated lung preparations. We hypothesized that methylene blue, a guanylate cyclase inhibitor, and N omega-nitro-L-arginine, a nitric oxide synthase inhibitor, would increase pulmonary vascular tone and improve gas exchange in anesthetized and ventilated (inspired O2 fraction 0.4) dogs with oleic acid (OA) lung injury. Mean pulmonary arterial pressure-(Ppa) flow (Q) relationships (generated by a manipulation of venous return, which was increased by opening a femoral arteriovenous bypass or decreased by inflating an inferior vena cava balloon) and gas exchange (evaluated by arterial blood gases and SF6 intrapulmonary shunt determinations) were investigated before and after OA (0.06 ml/kg i.v.) and again after solvent (n = 8), methylene blue (8 mg/kg i.v., n = 10), or N omega-nitro-L-arginine (40 mg/kg i.v., n = 8) in a randomized order. OA administration induced pulmonary hypertension, decreased arterial PO2, and increased intrapulmonary shunt. After OA, solvent had no effect on pulmonary hemodynamics and gas exchange. Both methylene blue and N omega-nitro-L-arginine further increased Ppa at all levels of Q. Only methylene blue, however, improved gas exchange after OA (arterial PO2 from 71 +/- 6 to 89 +/- 12 Torr and intrapulmonary shunt from 44 +/- 6 to 34 +/- 6%, both P < 0.02). These results suggest that nitric oxide is released during OA lung injury and modulates pulmonary hypertension. Whether nitric oxide impairs the regulation of gas exchange in OA lung injury remains uncertain, however.

Simultaneous measurement of fluid and protein permeability in isolated rabbit lungs during edema.

Fluid conductance and protein permeability have been studied in isolated perfused lung models of pulmonary edema. However, previous studies have not investigated changes of both fluid conductance and protein permeability in the same isolated lung preparation after injury. Arachidonic acid (AA) metabolites are involved in the inflammatory processes that lead to the development of pulmonary edema. The hemodynamic effects of AA have been well established; however, controversy exists concerning the ability of AA to alter the permeability of the pulmonary microvasculature to fluid and protein. The purpose of this study was to simultaneously determine whether transvascular fluid conductance and protein permeability are increased in isolated perfused rabbit lungs with pulmonary edema induced by AA. Indomethacin (80 microM) was added to the perfusate to inhibit the hemodynamic effects of AA and produce a pressure-independent model of pulmonary edema. Fluid conductance was assessed by determination of the capillary filtration coefficient (Kf), and protein permeability was evaluated by measurement of 125I-albumin clearance. The injection of AA (3 mg/200 ml of perfusate) into the pulmonary arterial catheter resulted in an increase in lung weight over the remaining 30-min experimental period. Kf (microliter.s-1 x cmH2O-1 x g dry lung-1) was increased (P < 0.05) in AA-treated lungs at 10 and 30 min post-AA injection when compared with control lungs and baseline values (determined 10 min before AA injection). Albumin clearance was also greater (P < 0.05) in lungs that received AA. 125I-albumin clearance was measured at different rates of fluid flux produced by elevation of venous pressure.(ABSTRACT TRUNCATED AT 250 WORDS)

Pulmonary vascular reactivity and hemodynamic changes in elastase-induced emphysema in hamsters

Changes in pulmonary hemodynamics and vascular reactivity in emphysematous hamsters were studied in an isolated lung preparation perfused at constant flow with blood and 3% dextran. Hamsters were treated with intratracheal porcine pancreatic elastase at 70 days of age, and experimental studies were conducted at 1, 3, and 8 mo after treatment. Baseline pulmonary arterial pressure in elastase-treated lungs was increased compared with saline-treated control lungs 1 mo after treatment, but this increase did not progress at 3 and 8 mo. Increases in pulmonary arterial pressure in elastase-treated lungs were temporally correlated with the morphological development of emphysema and right ventricular hypertrophy; both of these were evident at 1 mo after treatment and showed little change thereafter. Pressor responses to hypoxia and angiotensin II were not different between elastase-treated and control lungs at 1 and 3 mo. At 8 mo, however, pressor responses in emphysematous lungs to 0% O2 (but not to angiotensin II) were significantly increased. This was the result of a lack of the normal age-related fall in the hypoxic pressor response. Our results suggest that the right ventricular hypertrophy found in these emphysematous animals results from a chronically increased pulmonary vascular resistance. Furthermore, increases in pulmonary vascular resistance in the early development of emphysema are likely a result of the loss of vascular beds and supporting connective tissue.

Recurrent episodes of gram-negative bacteremia or endotoxemia change reactivity of pre- and post-capillary pulmonary segments to angiotensin or free radicals.

Recurrent episodes of Gram-negative bacteremia (from intraperitoneal abscesses) or endotoxemia cause lung microvascular injury in the rat. Change in vascular reactivity was assessed in response to challenge. In the isolated lung preparation, resistance was partitioned between pre-(PVRa) and post-capillary (PRVv) segments: vasoreactivity was assessed by challenge with Angiotensin II (AII) or reactive oxygen metabolites. Animals received 4 weekly intra-abdominal implants of live E. coli and B. fragilis in a carrier of sterile cecal content and barium sulfate (SEPSIS) or carrier alone (SHAM SEPSIS): or 4 weekly intravenous infusion of E. coli endotoxin (ENDO) or of saline (SHAM ENDO). A fifth group were untreated controls (CONTROL). In the SEPSIS and ENDO lungs, PVRa and PVRv before challenge were normal. In the SEPSIS lung, AII increased PVRa more than in the control lung, PVRv to a similar degree in both. In the ENDO lung it increased PVRa compared with its effect on the SHAM ENDO lung: In both it also increased PVRv, to a similar degree and well above the baseline. Always tachyphylaxis developed with increases in dosage (to 25 microns and 50 microns, respectively). Oxygen free radical challenge in the SEPSIS and ENDO lung caused significant vasoconstriction, particularly PVRv, whereas no response was observed in the CONTROL or SHAM-treated lung from either group. Abnormal lung vascular reactivity after SEPSIS or ENDOTOXIN is evident on challenge, the two agents used here detecting site specific changes.

Differential effects of alveolar and arterial oxygen tension on pulmonary vasomotor tone in ECMO-perfused, isolated piglet lungs

Hypoxia is a known stimulant of pulmonary hypertension. We hypothesized graded effects of alveolar (PAO2) and arterial (PaO2) oxygen tension on pulmonary vascular resistance (PVR). A standard in situ, isolated lung preparation was modified by adding an oxygenator to the perfusion circuit with cannulation of the unarrested heart, allowing control of PAO2 and PaO2 in lungs devoid of ischemic injury. Seven anesthetized piglets were prepared with occlusive tracheostomy, ductus arteriosus ligation, and cannulation of the left atrium and main pulmonary artery. Animals were exsanguinated while simultaneously perfusing the lungs with a donor-blood primed extracorporeal membrane oxygenation circuit. Flow, left atrial pressure, pH, and PCO2 were kept constant. PAO2 and PaO2 were altered to establish four different experimental conditions as described by a latin square. PVR was calculated from measurements of pulmonary artery pressure (PAP) before and after introducing an experimental condition. Results show that (1) alveolar hypoxia significantly increases PVR despite arterial hyperoxia; (2) alveolar hypoxia is a more potent stimulus of pulmonary vasoconstriction than arterial hypoxemia; (3) alveolar and arterial oxygen tension are independent, additive effectors of PVR; and (4) recovery from acute hypoxic pulmonary vasoconstriction may be more sensitive to alveolar oxygen tension.

Antigen-Induced Contraction of Human Isolated Lung Preparations Passively Sensitized with Monoclonal IgE: Effects of Indomethacin

Human isolated lung preparations were passively sensitized using mouse monoclonal dinitrophenyl (DNP)-specific IgE antibodies. The contractile response to antigen (DNP-bovine serum albumin; DNP-BSA) was approximately 80% of the histamine response (50 microM: 0.20 +/- 0.03 g/mm2) in bronchial muscle preparations. In passively sensitized pulmonary vascular and parenchymal preparations, the contraction to antigen was negligible. Indomethacin (1.7 microM; 30 min) did not alter the contractile response to DNP-BSA (5 micrograms/ml) in bronchial tissues. In passively sensitized bronchial muscle preparations stimulated with DNP-BSA, there was a significant increase (2-fold) in prostanoid production. This production was inhibited by indomethacin. These data suggest that endogenous prostaglandins may not play a role in the regulation of human isolated bronchial muscle contraction to antigen in vitro.