Impact of platelet activating factor on vascular responsiveness in isolated rat lungs

Platelet activating factor (PAF), a suspected mediator of acute lung injury, has been shown to potentiate contraction in isolated porcine carotid arteries. Such an action of PAF, if it occurred in the pulmonary circulation, could be of significance to the evolution of pulmonary hypertension in acute lung injury. Accordingly, we used isolated rat lungs perfused at a constant flow rate with physiologic salt solution to test the hypothesis that PAF-induced lung injury is associated with pulmonary vascular hyperresponsiveness to constrictor stimuli. PAF in concentrations of 0.1 to 10 ng/ml failed to influence pressor responses evoked by i.a. bolus injections of angiotensin II (Ang II) whereas 1 micrograms/ml of PAF significantly blunted Ang II-induced vasoconstriction. Similarly, 1 micrograms/ml, but not 0.1 ng/ml, of PAF attenuated constriction induced by ventilation with 3% O2. PAF at all concentrations tested failed to influence pressor responses evoked by i.a. bolus injections of KCI. Concentrations of PAF which blunted Ang II and hypoxic responses were associated with increased lung wet-to-dry weight ratios indicative of pulmonary edema. Another agent that provokes edema, cytochalasin B, also increased lung wet-to-dry weight ratios and blunted Ang II-, hypoxia-, and KCI-induced pressor responses. PAF delivered as i.a. bolus injections caused acute vasodilation in preparations preconstricted with Ang II but not in those preconstricted with KCI. Collectively, these observations demonstrate that PAF fails to augment and instead blunts pulmonary vascular responsiveness to pressor stimuli, possibly by mechanisms that relate to PAF-induced edema formation and/or vasodilation.     

血液透析诱发肺水肿-肺型失衡综合征的实验研究

目的证明快速透析诱发的失衡综合征(DDS)伴发肺水肿的发病机制.方法采急性肾衰竭犬模型,评定快速血液透析后血清和脑脊液生化参数、颅内压、肺血管阻力指数、脑/肺组织干湿比、肺水肿指数和脑与肺组织学变化.结果透析快速排除尿素氮、肌酐导致DDS,表现为颅压增高和发生神经系统症状.监测C组ARF狗血流动力学参数,显示为透析后肺动脉压(PAP)、肺毛细血管嵌楔压(PCWP)、右房压(RAP)、右室压(RVP)、中心静脉压(CVP)增加;随透析时间的延长,肺血管总阻力(TPRI)、颅内压增加;透析后肺水肿指数增加,脑、肺组织干湿比减少以及脑、肺组织学检查均提示脑和肺水肿.D组狗假透析后没有上述变化.结论实验结果表明血液透析可以诱发肺和脑水肿,其发生机制可能是因血浆尿素浓度快速下降有关,通过"尿素逆渗透效应"导致血浆/组织产生渗透梯度,使血浆水进入脑和肺组织,临床可出现脑水肿、肺水肿等多系统失衡现象.     

Bleomycin-induced acute lung injury in the rat does not influence pulmonary vascular responsiveness in vitro.

OBJECTIVE: To investigate the effects of the intratracheal and iv administration of bleomycin on the contraction and endothelially dependent vasodilation of rat pulmonary arteries in vitro. DESIGN: Prospective pharmacologic study. SETTING: National Heart and Lung Institute, London, UK. INTERVENTIONS: Intratracheal saline, intratracheal and iv bleomycin. MEASUREMENTS AND MAIN RESULTS: Rats treated with intratracheal bleomycin developed a significant increase in mean lung wet/dry weight ratio (5.6 +/- 0.4 [SEM] vs. 3.9 +/- 0.1, p less than .05) when compared with saline-treated control animals, confirming the development of pulmonary edema. However, these rats displayed normal relaxant responses to the endothelially dependent vasodilator acetylcholine and a normal contractile response to phenylephrine in vitro. Intravenous bleomycin had no effect on either wet/dry weight ratio or the response to either drug. CONCLUSIONS: Despite evidence for the loss of endothelial integrity that characterizes lung injury after intratracheal bleomycin, isolated pulmonary artery rings in vitro showed no loss of endothelial cell function. The role of the endothelium in modulating pulmonary ventilation/perfusion matching after lung injury is unclear.     

Primed stimulation of isolated perfused rabbit lung by endotoxin and platelet activating factor induces enhanced production of thromboxane and lung injury.

Bacterial sepsis often precedes the development of the adult respiratory distress syndrome (ARDS) and bacterial endotoxin (LPS) produces a syndrome similar to ARDS when infused into experimental animals. We determined in isolated, buffer-perfused rabbit lungs, free of plasma and circulating blood cells that LPS synergized with platelet activating factor (PAF) to injure the lung. In lungs perfused for 2 h with LPS-free buffer (less than 100 pg/ml), stimulation with 1, 10, or 100 nM PAF produced transient pulmonary hypertension and minimal edema. Lungs perfused for 2 h with buffer containing 100 ng/ml of Escherichia coli 0111:B4 LPS had slight elevation of pulmonary artery pressure (PAP) and did not develop edema. In contrast, lungs exposed to 100 ng/ml of LPS for 2 h had marked increases in PAP and developed significant edema when stimulated with PAF. LPS treatment increased capillary filtration coefficient, suggesting that capillary leak contributed to pulmonary edema. LPS-primed, PAF-stimulated lungs had enhanced production of thromboxane B2 (TXB) and 6-keto-prostaglandin F1 alpha (6KPF). Indomethacin completely inhibited PAF-stimulated production of TXB and 6KPF in control and LPS-primed preparations, did not inhibit the rise in PAP produced by PAF in control lungs, but blocked the exaggerated rise in PAP and edema seen in LPS-primed, PAF-stimulated lungs. The thromboxane synthetase inhibitor dazoxiben, and the thromboxane receptor antagonist, SQ 29,548, similarly inhibited LPS-primed pulmonary hypertension and edema after PAF-stimulation. These studies indicate that LPS primes the lung for enhanced injury in response to the physiologic mediator PAF by amplifying the synthesis and release of thromboxane in lung tissue.     

Bleomycin-induced lung injury in rats selectively abolishes hypoxic pulmonary vasoconstriction: evidence against a role for platelet-activating factor.

1. The role of platelet-activating factor in the attenuated hypoxic pulmonary vasoconstriction associated with lung injury was evaluated using specific platelet-activating factor antagonists and an isolated perfused lung preparation. 2. Intratracheal bleomycin was administered to rats to produce acute lung injury. Animals received intratracheal saline (control), intratracheal bleomycin or the platelet-activating factor antagonists BN 52021, WEB 2170 or WEB 2086 before and after bleomycin treatment. Forty-eight hours after intratracheal administration of bleomycin or saline the animals were killed. 3. The increases in pulmonary artery pressure during two periods of hypoxic ventilation and in response to 0.2 microgram of angiotensin II were measured. Acetylcholine-induced vasodilatation after pre-constriction with prostaglandin F2 alpha was also measured. To quantify lung injury, the wet/dry ratio of lung weight was determined. 4. Bleomycin treatment attenuated the first and second hypoxic pressor responses by 93% and 77%, respectively, but not the pressor response to angiotensin II nor the vasodilator response to acetylcholine. BN 52021 plus bleomycin augmented the first hypoxic pressor response compared with bleomycin treatment alone, but the structurally unrelated platelet-activating factor antagonists WEB 2170 and WEB 2086 had no significant effect on the bleomycin-induced attenuation of hypoxic pulmonary vasoconstriction. None of the platelet-activating factor antagonists blocked the increase in the wet/dry lung weight ratio induced by bleomycin. 5. Bleomycin-induced lung injury selectively attenuates hypoxic pulmonary vasoconstriction, an effect that does not appear to be mediated by platelet-activating factor. The mechanism remains to be elucidated, but may involve destruction of the hypoxic 'sensor' within the respiratory tract.     

Plasma and lipids from stored packed red blood cells cause acute lung injury in an animal model.

Transfusion-related acute lung injury (TRALI) is a serious complication of hemotherapy. During blood storage, lipids are generated and released into the plasma. In this study, the role of these lipids in TRALI was investigated using an isolated, perfused rat lung model. Rats were pretreated with endotoxin (LPS) or saline in vivo and the lungs were isolated, ventilated, and perfused with saline, or (a) 5% (vol/ vol) fresh human plasma, (b) plasma from stored blood from the day of isolation (D.0) or from the day of outdate (D.42), (c) lipid extracts from D.42 plasma, or (d) purified lysophosphatidylcholines. Lungs from saline or LPS-pretreated rats perfused with fresh (D.0) plasma showed no pulmonary damage as compared with saline perfused controls. LPS pretreatment/D.42 plasma perfusion caused acute lung injury (ALI) manifested by dramatic changes in both pulmonary artery pressure and edema. Incubation of LPS pre-tx rats with mibefradil, a Ca2+ channel blocker, or WEB 2170, a platelet-activating factor (PAF) receptor antagonist, inhibited ALI caused by D.42 plasma. Lung histology showed neutrophil sequestration without ALI with LPS pretreatment/saline or D.0 plasma perfusion, but ALI with LPS pretreatment/D.42 plasma perfusion, and inhibition of D.42 plasma induced ALI with WEB 2170 or mibefradil. A significant increase in leukotriene E4 was present in LPS-pretreated/D.42 plasma-perfused lungs that was inhibited by WEB 2170. Lastly, significant pulmonary edema was produced when lipid extracts of D.42 plasma or lysophosphatidylcholines were perfused into LPS-pretreated lungs. Lipids caused ALI without vasoconstriction, except at the highest dose employed. In conclusion, both plasma and lipids from stored blood produced pulmonary damage in a model of acute lung injury. TRALI, like the adult respiratory distress syndrome, may be the result of two insults: one derived from stored blood and the other from the clinical condition of the patient.     

Platelet-activating factor (PAF) receptor-mediated calcium mobilization and phosphoinositide turnover in neurohybrid NG108-15 cells: studies with BN50739, a new PAF antagonist.

Platelet-activating factor (PAF) is an unusually potent lipid autacoid with a variety of biological activities. The growing body of evidence suggests that PAF might play an important role in modulation of central nervous system function, particularly during ischemia- and trauma-induced neuronal damage. However, the mechanisms involved in PAF actions on neuronal or other brain cells is virtually unknown. Therefore, this study was designed to characterize PAF receptor-mediated cellular signal transduction in neurohybrid NG108-15 cells with the aid of a new potent PAF antagonist, BN 50739. PAF induced an immediate and concentration-dependent increase in [Ca++]i with an EC50 of 6.8 nM. PAF-induced [Ca++]i mobilization was inhibited by several structurally unrelated PAF antagonists such as BN 50739, WEB 2086, SRI 63-441 and BN 52021, in a dose-dependent manner with IC50 values of 4.8, 6.9, 809 and 98500 nM, respectively. The calcium channel blockers nifedipine (5 microM) and diltiazem (10 microM) had no effect on the PAF-induced increase in [Ca++]i, but omission of CA++ from the incubation buffer caused an 82% reduction of PAF-induced [Ca++]i elevation; the remainder contributed from intracellular sources was completely inhibited by 10 microM TMB-8, an intracellular Ca++ blocker. NG108-15 cells exhibited homologous desensitization to sequential addition of PAF, but no heterologous desensitization between PAF and other agonists such as bradykinin, endothelin, angiotensin II and ATP was observed. PAF stimulated phosphoinositide metabolism in a dose-dependent manner with an EC50 of 5.1 nM for IP3 formation, which was also inhibited by the PAF antagonist BN 50739 in a dose-dependent manner (IC50 = 3.6 nM).(ABSTRACT TRUNCATED AT 250 WORDS)     

Salutary effects of prostaglandin E1 in perfused rat lungs injured with hydrogen peroxide

Studies were conducted in isolated, buffer-perfused rat lungs to determine if prostaglandin (PG) E1 attenuated pulmonary edema provoked by hydrogen peroxide (H2O2). When lungs were challenged by 60 min of perfusion with H2O2 (generated by the reaction between glucose and glucose oxidase) the wet weight-to-dry weight ratio increased from control by 54%, indicating development of pulmonary edema. In contrast, lungs treated simultaneously with H2O2 plus PGE1 (1 microgram/min) failed to exhibit an elevated wet-to-dry weight ratio. H2O2-injured lungs demonstrated a modest 2 torr increase in pulmonary arterial perfusion pressure that was not influenced by simultaneous treatment with PGE1. Both radioimmunoassay (RIA) and high-performance liquid chromatographic (HPLC) analysis detected increased amounts of (5S)-5-hydroxy-6,8,11,14 eicosatetraenoic acid in the perfusion medium of H2O2-injured lungs (RIA, 48.0 +/- 14.7; HPLC, 54.8 +/- 13.5) relative to controls (RIA, 6.6 +/- 1.6; HPLC, 6.8 +/- 1.9), and simultaneous treatment with PGE1 tended to blunt this increase (RIA, 29.2 +/- 8.3; HPLC, 29.8 +/- 7.6). PGE1 abolished the increase in wet weight-to-dry weight ratio induced by exogenous leukotriene C4. Production of H2O2 by the glucose-glucose oxidase reaction was not influenced by PGE1. Taken together, these observations indicate that PGE1 attenuates H2O2-induced pulmonary edema formation in buffer-perfused rat lungs by mechanisms that may relate to inhibition of lung 5'-lipoxygenase activation and/or to inhibition of the injurious effects of endogenously produced lipoxygenase products.     

Platelet activating factor mediates interleukin-2-induced lung injury in the rat.

Interleukin-2 was recently shown to cause acute lung injury characterized by microvascular permeability defect, interstitial edema, and leukosequestration. Similar responses can also be produced by platelet activating factor (PAF). Thus, the present study aimed to examine whether PAF plays a key role in the development of IL-2-induced lung injury in the anesthetized rat. Intravenous infusion (60 min) of recombinant human IL-2 at 10(5)-10(6) U/rat (n = 7-9) dose-dependently elevated lung water content (27 +/- 1%, P less than 0.01), myeloperoxidase activity (+84 +/- 23%, P less than 0.05), and serum thromboxane B2 (990 +/- 70%, P less than 0.01), but failed to alter blood pressure, hematocrit, serum tumor necrosis factor-alpha, and circulating leukocytes and platelets. Pretreatment (-30 min) with a potent and specific PAF antagonist, BN 50739 (10 mg/kg, intraperitoneally, n = 6) prevented the pulmonary edema (P less than 0.05) and thromboxane B2 production (P less than 0.01), and attenuated the elevation of lung myeloperoxidase activity (+18 +/- 16%, P less than 0.05) induced by IL-2. These data suggest that PAF is involved in the pathophysiological processes leading to IL-2-induced lung injury, and point to the potential therapeutic capacity of PAF antagonists in preventing pulmonary edema during IL-2 therapy.     

Role of platelet activating factor in propagation of cardiac damage during myocardial ischemia

The role of platelet activating factor (PAF) in acute myocardial ischemia (MI), produced by the ligation of the left main coronary artery, was studied in anesthetized rats. A significant loss of cardiac amino-nitrogen concentration and cathepsin D activity was observed 6 hr after permanent occlusion MI or 10 min of MI followed by 6 hr of reperfusion in rats. A novel, potent, PAF antagonist, CV-6209 (160 nmol/kg or 1.6 mumol/kg) injected after the ligation, significantly retarded the loss of amino-nitrogen and cathepsin D activity in a dose-related manner. In another group of rats, CV-6209 (1.6 mumol/kg) significantly blocked the hypotension induced by repetitive injections of PAF (570 pmol/kg) with an apparent half-life of approximately 180 min. In isolated rat hearts perfused with Krebs-Henseleit solution, PAF (25 nmol/l) significantly increased coronary perfusion pressure by 15 +/- 2 mmHg and induced an increase in cardiac permeability using fluorescein isothiocyanate bovine albumin as a marker. Furthermore, the increase in cardiac permeability induced in isolated perfused rat hearts undergoing 15 min global ischemia followed by reperfusion was significantly attenuated by CV-6209 (250 nmol/l). These data indicate that PAF is an important mediator of ischemic damage in rat MI. Moreover, the extension of ischemic damage may be enhanced by the increase in cardiac permeability induced by PAF.     

Tetrahydrobiopterin prevents platelet-activating factor-induced intestinal hypoperfusion and necrosis: Role of neuronal nitric oxide synthase

OBJECTIVE: We reported previously that neuronal nitric oxide synthase (nNOS) is the predominant NOS in rat small intestine and is down-regulated by platelet-activating factor (PAF). The severity of the bowel injury induced by PAF is inversely related to its suppressing effect on nNOS. Here, we investigated whether intestinal perfusion is regulated by nNOS and whether tetrahydrobiopterin, a co-factor and stabilizer of nNOS, reverses PAF-induced intestinal hypoperfusion and injury. SETTING: Animal laboratory. DESIGN: We first examined nNOS regulation of splanchnic blood flow by measuring the perfusion of the heart, lung, ileum, and kidney in rats after a nNOS inhibitor. We then examined the protective effect of tetrahydrobiopterin on PAF-induced bowel injury, mesenteric hypoperfusion, and systemic inflammation. SUBJECTS: Adult male Sprague-Dawley rats. INTERVENTION: In part 1 of the experiment, rats were given 7-nitroindazole (a specific nNOS inhibitor, 50 mg.kg.day). In part 2 of the experiment, rats were treated with tetrahydrobiopterin (20 mg/kg) 5 mins before and 30 mins after PAF challenge (2.2 microg/kg, intravenously) MEASUREMENTS: Perfusion of the heart, lung, ileum, and kidney was measured at 1 and 4 days after 7-nitroindazole, using fluorescent microspheres. Intestinal injury and inflammation (myeloperoxidase content), blood perfusion, calcium dependent-NOS activity, and systemic inflammation (hypotension and hematocrit increase) were assessed 1 hr after PAF with and without tetrahydrobiopterin treatment. RESULTS: In part 1 of the experiment, 7-nitroindazole induced a long-lasting reduction of blood perfusion and inducible NOS expression selectively in the ileum but not in nonsplanchnic organs such as heart, lungs, and kidneys. In part 2, tetrahydrobiopterin protected against PAF-induced intestinal necrosis, hypoperfusion, neutrophil influx, and NOS suppression. It also reversed hypotension and hemoconcentration. Sepiapterin (2 mg/kg, stable tetrahydrobiopterin precursor) also attenuated PAF-induced intestinal injury. CONCLUSIONS: We conclude that nNOS selectively regulates intestinal perfusion. Tetrahydrobiopterin prevents PAF-induced intestinal injury, probably by stabilizing nNOS and maintaining intestinal perfusion.     

Evidence against a role for platelet-activating factor in hypoxic pulmonary vasoconstriction in the rat

1. The effect of two structurally different platelet-activating factor (PAF) receptor antagonists, WEB 2086((3-[4-(2-chlorophenyl)-9-methyl-6H-thieno[3,2-f]-[1,2,4]- treazolo-[4,3-alpha][1,4]-diazepine-2-yl]-1-(morpholinyl)-1- propanone)) and BN 52021, on hypoxic pulmonary vasoconstriction (HPV) was studied using an isolated rat lung preparation perfused with blood. 2. In lungs treated with WEB 2086 there was a dose-dependent attenuation of HPV, with complete abolition of HPV at the maximum dose. 3. Low doses of WEB 2086 caused only slight diminution of the pressor response to angiotensin II, although higher doses caused increasing attenuation of the angiotensin pressor response. 4. BN 52021 did not affect HPV. 5. Injection of PAF caused an increase in pulmonary artery pressure of 145%, a response abolished by pretreatment of the lungs with either WEB 2086 or BN 52021. 6. These results suggest that PAF does not mediate HPV in the rat.     

吸入米力农对油酸诱导大鼠急性肺损伤的作用

摘要：目的 观察超声雾化吸入米力农对油酸诱导大鼠急性肺损伤（acute lung injury，ALI）的影响。方法 采用静脉注射油酸复制ALI大鼠模型。将40 只SD 大鼠随机分为4 组:对照组（I组）、ALI组（II组）、米力农雾化吸入高剂量组（III组）和米力农雾化吸入低剂量组（IV组）。实验过程中每隔60分钟记录大鼠血压（BP）、肺动脉压（PAP），测定动脉血气和混合静脉血气。注射油酸240分钟后检测肺湿干比(W/D)、髓过氧化物酶（myeloperoxidase，MPO），并且对肺组织进行光镜和电镜观察。结果 超声雾化吸入米力农组中由于注射油酸引起的PAP升高、肺内分流(Qs/Qt)增加和PaO2/FiO2下降均得到缓解，高剂量组更为明显。各治疗组肺W/D 和MPO均比对照组降低，高剂量组更为明显。光镜和电镜观察III、IV组肺损伤有不同程度改善。 结论 米力农雾化吸入能够缓解油酸引起的低氧血症，有效改善ALI多项指标。其对ALI的治疗作用具有剂量依赖性。     

烟雾吸入致伤犬右侧肺引发左侧肺损伤的实验研究

目的：探讨烟雾致伤犬一侧肺对另侧肺的影响及其机制。方法：在Olympus(型号P10）纤维支气管镜引导下直视行双腔管气道插管,烟雾吸入致伤犬右侧肺,分别采用AVL990型自动血气分析仪、干湿重法、过氧化氢还原法、微量酸滴定法、TBA法、生物测定法检测犬动脉血气、肺含水量、髓过氧化物酶（MPO）活性、磷脂酶A2（PLA2）活性、脂质过氧化物丙二醛（MDA）及血小板活化因子（PAF）含量。结果：右侧肺烟雾吸入致伤后,犬呼吸频率明显增快,动脉血氧分压（PaO2)进行性下降,24小时达8．37kPa(1kPa=7.5mmHg)。但动脉血二氧化碳分压（PaCO2)仅24小时点与伤前比较显著升高。进一步研究发现,烟雾致伤后右侧肺后24小时,左侧肺含水量明显增加,粒细胞标志酶MPO活性、膜磷脂分解酶PLA2活性、炎性介质PAF及MDA含量与正常对照组比较均显著升高。病理检查见,致伤犬双肺弥漫性肺泡内水肿,间隔增厚,伴大量炎细胞浸润,惟左侧肺略轻。结论：烟雾吸入致伤犬一侧肺可引起另侧肺水肿,其机制与另侧肺组织继发性的白细胞浸润、PLA2活化、脂质过氧化损伤及炎性介质PAF增加有关。     

Acetyl glyceryl ether phosphorylcholine-stimulated human platelets cause pulmonary hypertension and edema in isolated rabbit lungs. Role of thromboxane A2.

Macrophages, neutrophils, and platelets may play a role in acute edematous lung injury, such as that seen in the adult respiratory distress syndrome (ARDS), but their potential actions and interactions are unclear. Because stimulated human macrophages and neutrophils can release acetyl glyceryl ether phosphorylcholine (AGEPC), a potent platelet activator, we hypothesized that in ARDS, leukocyte release of AGEPC might stimulate platelets to release thromboxane A2 (TXA2), which then produces pulmonary hypertension and lung edema. In support of this premise, we found that pulmonary hypertension and edema occurred in isolated rabbit lungs perfused with human platelets and AGEPC, but not with platelets or AGEPC alone. Infusion of a vasodilator (nitroglycerin) to maintain base-line pulmonary artery pressures in lungs perfused with platelets and AGEPC prevented the development of lung edema suggesting that platelet and AGEPC-induced edema was hydrostatic in nature. Additional experiments suggested that the increased pressure was a result of TXA2 release from platelets stimulated by AGEPC. Specifically, preincubation of platelets with imidazole, a thromboxane synthetase blocker, prior to infusion with AGEPC significantly diminished pulmonary hypertension and prevented lung edema. Furthermore, pretreating lung preparations with 13-azaprostanoic acid, a TXA2 antagonist, before infusion of AGEPC and untreated platelets also reduced the pulmonary hypertension and blocked the lung edema. The role of TXA2 was further suggested when perfusates from lungs infused with platelets and AGEPC developed high levels of TXA2, whereas perfusates from controls did not. These results suggest that platelet aggregation induced by AGEPC may contribute to ARDS by releasing TXA2, which raises microvascular pressure and increases edema formation, especially when an underlying permeability defect is present.     

Effects of L-652,731, a platelet-activating factor (PAF) receptor antagonist, on PAF- and complement-induced pulmonary hypertension in sheep

Thromboxane-mediated pulmonary hypertension, pulmonary edema, arterial hypoxia and pulmonary leukostasis occur in response to the infusion of plasma containing zymosan-activated complement (ZAP) in sheep. Platelet-activating factor (PAF) is a potential mediator of some of these effects. We investigated the effects of PAF infusions in unanesthetized sheep and the effects of the PAF receptor antagonist L-652,731 [trans-2,5-bis(3,4,5-trimethoxyphenyl)tetrahydrofuran] on the hematologic, hemodynamic and biochemical alterations produced by infusions of both ZAP and PAF. Infusions of 2 to 20 micrograms of PAF in 0.25% ovine serum albumin-saline produced pulmonary hypertension, hypoxia and dose-dependent thrombocytopenia, neutropenia and thromboxane synthesis. The effects of a 2 micrograms of PAF infusion were both qualitatively and quantitatively similar to those produced by a ZAP infusion. Pretreatment with aspirin (10 mg/kg) protected the sheep against the pulmonary vascular response to 20 micrograms of PAF and blocked completely the thromboxane synthesis. L-652,731 at a dose of 8 mg/kg blocked completely the neutropenia, thrombocytopenia, thromboxane synthesis, pulmonary hypertension and hypoxia induced by 5 micrograms of PAF, but this protective effect was not observed in animals infused with ZAP. These results indicate that PAF is probably not a mediator of the neutropenia, thromboxane-mediated pulmonary hypertension and hypoxia which result from the infusion of ZAP into sheep.     

隔离肺灌注模型的动物实验研究

目的 成功建立隔离肺灌注化疗的动物模型。方法 建立兔隔离单肺灌注系统，使用阿霉素进行灌注化疗，并应用荧光分光光度法检测双肺及心、肝、肾组织中阿霉素含量及肺湿／干重量比。结果 隔离灌注肺的阿霉素含量较对照肺及心、肝、肾组织显著升高；而肺湿／干重量比则无明显差别。结论 我们使用的隔离肺灌注系统可在肺组织局部得到较高的化疗药物浓度，且未出现急性肺损伤，使用该模型治疗肺癌及肺转移癌应可取得较好效果。     

Exacerbation by granulocyte colony-stimulating factor of prior acute lung injury: implication of neutrophils

OBJECTIVE: Granulocyte colony-stimulating factor is widely prescribed to hasten recovery from cancer chemotherapy-induced neutropenia and has been reported to induce pulmonary toxicity. However, circumstances and mechanisms of this toxicity remain poorly known. DESIGN: To reproduce a routine situation in cancer patients receiving chemotherapy, we investigated the mechanisms underlying granulocyte colony-stimulating factor-induced exacerbation of alpha-naphthylthiourea-related pulmonary edema. SETTING: Laboratory research unit. SUBJECTS: Male specific-pathogen-free Sprague-Dawley rats. INTERVENTIONS: The effects of granulocyte colony-stimulating factor given alone or after alpha-naphthylthiourea used to induce acute lung injury were investigated. MEASUREMENTS AND MAIN RESULTS: Lung injury was assessed based on neutrophil sequestration (myeloperoxidase activity in lung tissue) and influx into alveolar spaces (bronchoalveolar lavage fluid cell quantification) and on edema formation (wet/dry lung weight ratio) and alveolar protein concentration into bronchoalveolar lavage fluid. Tumor necrosis factor-alpha and interleukin-1beta were measured in serum, lung homogenates, and isolated alveolar macrophage supernatants. In control rats, granulocyte colony-stimulating factor (25 microg/kg) significantly elevated circulating neutrophil counts without producing alveolar recruitment or pulmonary edema. alpha-Naphthylthiourea significantly increased the wet/dry lung weight ratio (4.68 +/- 0.04 vs. 4.38 +/- 0.07 in controls, p=.04) and induced alveolar protein leakage. Adding granulocyte colony-stimulating factor to alpha-naphthylthiourea exacerbated pulmonary edema, causing neutrophil sequestration in pulmonary vessels, significantly increasing lung myeloperoxidase activity (12.7 +/- 2.0 mOD/min/g vs. 1.1 +/- 0.4 mOD/min/g with alpha-naphthylthiourea alone; p<.0001), and increasing proinflammatory cytokine secretion. alpha-Naphthylthiourea-related pulmonary edema was not exacerbated by granulocyte colony-stimulating factor during cyclophosphamide-induced neutropenia or after lidocaine, which antagonizes neutrophil adhesion to endothelial cells. Tumor necrosis factor-alpha and interleukin-1beta concentrations in alveolar macrophage supernatants and lung homogenates were significantly higher with alpha-naphthylthiourea + granulocyte colony-stimulating factor than with either agent alone, and anti-tumor necrosis factor-alpha antibodies abolished granulocyte colony-stimulating factor-related exacerbation of alpha-naphthylthiourea-induced pulmonary edema. In rats with cyclophosphamide-induced neutropenia, tumor necrosis factor-alpha concentrations in alveolar macrophage supernatants and lung homogenates were significantly decreased compared with rats without neutropenia. CONCLUSION: Granulocyte colony-stimulating factor-related pulmonary toxicity may involve migration of neutrophils to vascular spaces, adhesion of neutrophils to previously injured endothelial cells, and potentiation of proinflammatory cytokine expression.     

Effect of mechanical ventilation on lung water volume in dogs

The effect of mechanical ventilation on lung water volume was studied in open-chest mongrel dogs with pulmonary edema. Pulmonary edema was induced by oleic acid infusion in 1 group and by elevating left atrial pressure in the other group. In both groups, 1 lung was ventilated mechanically, while the other lung was kept at a constant volume and not ventilated. In all dogs, the wet/dry ratio of the ventilated lung was significantly greater than that of the unventilated lung. This suggests that the difference in lung water volume between the ventilated lung and the nonventilated lung is due to lung volume.     

Reversible temperature-sensitive alterations in lung fluid balance

Hypothermia is intentionally imposed during the harvesting of lungs for transplantation. The aim of this study was to investigate the fluid balance alterations in rat lung preparations exposed to hypothermic perfusion. Lowering perfusate temperature from 37 degrees C to values between 27 and 7 degrees C caused an immediate, marked pulmonary hypertension and vasoconstriction accompanied by rapid development of pulmonary edema (+1.15 g, or approximately 90%, gain in lung weight within 5 min). However, on rewarming, vasoconstriction was immediately reversed. Edema was resolved, but along a two-component time course: an immediate reduction of lung weight on rewarming (t 1/2 of 0.5 min) that mirrored the recovery of pulmonary artery pressure and vasoconstriction, and also a slower pressure-independent component of recovery (t 1/2 of 3.5 min). Ouabain (300 microM) markedly inhibited the lung's ability to recover from edema, indicating that fluid clearance from lung tissue was the result of activation of ouabain-sensitive (Na+,K+)-ATPase pump. Results could not be explained by vascular or airspace injury as lung sections from hypothermic lungs appeared normal. The findings indicate that hypothermia induces pulmonary edema formation, which can be rapidly cleared upon rewarming by activation of ouabain-sensitive (Na+,K+)-ATPase pump. Thus, impaired fluid clearance from lung extravascular spaces may be a critical factor limiting gas exchange in transplanted lungs exposed to hypothermia.