Alpha-naphthyl-thiourea-induced pulmonary oedema in the rat: a topographical and electron-microscope study

Pinealectomy and melatonin administration in rats: their effects on pulmonary edema induced by α-naphthylthiourea

We aimed to observe the possible effects of melatonin (MLT) deprivation (pinealectomy) and exogenous MLT administration on pulmonary edema induced by alpha-naphthylthiourea (ANTU), a toxic chemical agent, in rats. Seventy animals were assigned to seven groups: control, sham pinealectomy (PINX), PINX, ANTU (10 mg/kg intraperitoneal on day 30), ANTU + MLT (10 mg/kg/day i.p. for 30 days), ANTU + PINX, and ANTU + PINX + MLT.In this study, pleural effusion (PE) formation, lung weight/body weight (LW/BW) and PE/BW ratios (fluid accumulation and weight values in the lungs) increase detected. Pre-ANTU MLT administration led to significant decreases in PE, LW/BW, and PE/BW levels. The inhibited glutathione (GSH) and superoxide dismutase (SOD) levels and high malondialdehyde (MDA) levels that ANTU increase lipid peroxidation in the study. MLT administration eliminated oxidative stress by reducing MDA and ameliorating GSH and SOD levels.Pre-ANTU MLT administration led to a significant decrease in interleukin-1 beta (IL-1β) and tumor necrosis factor-alpha (TNF-α) levels in the lung when compared to the ANTU group without MLT administration. Post-pinealectomy ANTU administration significantly increased IL-1β and TNF-α levels when compared to ANTU and MLT administration without pinealectomy. Diffused inflammatory cell infiltration, interstitial pulmonary edema, and histopathological congestion were observed after the administration of ANTU. Severity of the damage was elevated in the ANTU + PINX group. MLT treatment regressed pulmonary effusion and edema and improves lung structure. In brief, the findings suggested that MLT inhibited proinflammatory mediators and could serve as a therapeutic agent to prevent inflammatory disorders.

Impact of KvLQT1 potassium channel modulation on alveolar fluid homeostasis in an animal model of thiourea-induced lung edema

Alveolar ion and fluid absorption is essential for lung homeostasis in healthy conditions as well as for the resorption of lung edema, a key feature of acute respiratory distress syndrome. Liquid absorption is driven by active transepithelial sodium transport, through apical ENaC Na⁺ channels and basolateral Na⁺/K⁺-ATPase. Our previous work unveiled that KvLQT1 K⁺ channels also participate in the control of Na⁺/liquid absorption in alveolar epithelial cells. Our aim was to further investigate the function of KvLQT1 channels and their interplay with other channels/transporters involved in ion/liquid transport in vivo using adult wild-type (WT) and KvLQT1 knock-out (KO) mice under physiological conditions and after thiourea-induced lung edema. A slight but significant increase in water lung content (WLC) was observed in naïve KvLQT1-KO mice, relative to WT littermates, whereas lung function was generally preserved and histological structure unaltered. Following thiourea-induced lung edema, KvLQT1-KO did not worsen WLC or lung function. Similarly, lung edema was not aggravated by the administration of a KvLQT1 inhibitor (chromanol). However, KvLQT1 activation (R-L3) significantly reduced WLC in thiourea-challenged WT mice. The benefits of R-L3 were prevented in KO or chromanol-treated WT mice. Furthermore, R-L3 treatment had no effect on thiourea-induced endothelial barrier alteration but restored or enhanced the levels of epithelial alveolar AQP5, Na⁺/K⁺-ATPase, and ENaC expressions. Altogether, the results indicate the benefits of KvLQT1 activation in the resolution of lung edema, probably through the observed up-regulation of epithelial alveolar channels/transporters involved in ion/water transport.

Impact of ENaC downregulation in transgenic mice on the outcomes of acute lung injury induced by bleomycin

NEW FINDINGS

What is the central question of this study? How does the downregulation of ENaC, the major driving force for alveolar fluid clearance, impact acute lung injury outcomes induced by bleomycin, featuring alveolar damage, as observed during ARDS exudative phase? What is the main finding and its importance? ENaC downregulation in αENaC(-/-)Tg+ mice did not elicit a substantial worsening impact on the main bleomycin outcomes. In ARDS patients, both ENaC alteration and alveolar damage are observed. Thus, novel therapeutic avenues, favouring alveolar integrity restauration, in addition to lung oedema resolution capacity, mainly driven by ENaC, would be essential.

ABSTRACT

The exudative phase of acute respiratory distress syndrome (ARDS) is characterized by extended alveolar damage, resulting in accumulation of protein-rich inflammatory oedematous fluid in the alveolar space. Na⁺ reabsorption through ENaC channels is a major driving force for alveolar fluid clearance (AFC) in physiological and pathological conditions. It has previously been shown that partial αENaC impairment in transgenic (αENaC(-/-)Tg+) mice results in reduced AFC in basal conditions and increased wet/dry ratio after thiourea-induced lung oedema, a model in which the integrity of the alveolar epithelium is preserved. The goal of this study was to further investigate the impact of αENaC downregulation in αENaC(-/-)Tg+ mice using an experimental model of acute lung injury induced by bleomycin. A non-significant trend in enhanced weight loss and mortality rates was observed after the bleomycin challenge in αENaC(-/-)Tg+ compared to wild-type (WT) mice. Bronchoalveolar lavage analyses revealed increased TNFα levels and protein concentrations, as indexes of lung inflammation and alveolar damage, in αENaC(-/-)Tg+ mice, compared to WT, at day 3 post-bleomycin, although a statistical difference was no longer measured at day 7. Differential immune cell counts were similar in WT and αENaC(-/-)Tg+ mice challenged with bleomycin. Moreover, lung weight measurements indicated similar oedema levels in WT mice and in transgenic mice with impaired ENaC channels. Altogether, our data indicated that change in ENaC expression does not elicit a significant impact on lung oedema level/resolution in the bleomycin model, featuring alveolar damage.

Escherichia coli adhesion portion FimH functions as an adjuvant for cancer immunotherapy

Induction of antigen-specific immune activation by the maturation of dendritic cells (DCs) is a strategy used for cancer immunotherapy. In this study, we find that FimH, which is an Escherichia coli adhesion portion, induces toll-like receptor 4-dependent and myeloid differentiation protein 2-independent DC maturation in mice in vivo. A combined treatment regimen with FimH and antigen promotes antigen-specific immune activation, including proliferation of T cells, production of IFN-γ and TNF-α, and infiltration of effector T cells into tumors, which consequently inhibits tumor growth in mice in vivo against melanoma and carcinoma. In addition, combined therapeutic treatment of anti-PD-L1 antibodies and FimH treatment efficiently inhibits CT26 tumor growth in BALB/c mice. Finally, FimH promotes human peripheral blood DC activation and syngeneic T-cell proliferation and activation. Taken together, these findings demonstrate that FimH can be a useful adjuvant for cancer immunotherapy.

Effect of the endothelin receptor antagonist tezosentan on alpha-naphthylthiourea-induced lung injury in rats

Acute lung injury is an inflammatory syndrome that increases the permeability of the blood-gas barrier, resulting in high morbidity and mortality. Despite intensive research, treatment options remain limited. We investigated the protective efficacy of tezosentan, a novel, dual endothelin receptor antagonist, in an experimental model of alpha-naphthylthiourea (ANTU)-induced acute lung injury in rats. ANTU was intraperitoneally (i.p.) injected into rats at a dose of 10 mg/kg. Tezosentan was injected 30 minutes before ANTU was subcutaneously (s.c.) injected at doses of 2, 10, or 30 mg/kg, 60 minutes before ANTU was injected at doses of 2, 10, or 30 mg/kg (i.p.), and 90 minutes before ANTU at a dose of 10 mg/kg (i.p.). Four hours later, the lung weight/body weight (LW/BW) ratio and pleural effusion (PE) were measured. When injected 30 minutes before ANTU at doses of 2, 10, or 30 mg/kg (s.c.), tezosentan had no effect on lung pathology. When injected 60 minutes before ANTU at doses of 2, 10, or 30 mg/kg (i.p.) or 90 minutes before ANTU (10 mg/kg, i.p.), tezosentan significantly decreased the PE/BW ratio and had a prophylactic effect on PE formation at all doses. Therefore, tezosentan may attenuate lung injury. Furthermore, its acute and inhibitory effects on fluid accumulation were more effective in the pleural cavity than in the interstitial compartment in this experimental model.

Kinetics and determinants of the changes of CC16, a lung secretory protein in a rat model of toxic lung injury

PURPOSE

To investigate the kinetics and the determinants of the changes of the Clara cell 16 kDa protein (CC16) as a marker of lung injury following exposure to different toxicants.

METHODS

Rats were treated with 4-Ipomeanol (IPO), alpha-naphtylthiourea (ANTU), sodium chromate (Na(2)CrO(4)) or paraquat-(PQ). The changes of CC16, total protein, albumin, and cystatin-C were determined on BALF supernatan, and CC16, cystatin-C and creatinine levels were also determined in serum.

RESULTS

Bronchiolar insult due to IPO or ANTU resulted in an initial transient increase of serum CC16, parallel to that of albumin in BALF, and a subsequent reduction in both BALF and serum. A slight reduction of CC16 in BALF was already apparent one hour following treatment with PQ. In the serum, CC16 increased to 400% of basal value. With PQ and Na(2)CrO(4), the elevation of CC16 was mainly determined by the degree of renal impairment.

Influence of fructose-1,6-diphosphate on endotoxin-induced lung injuries in sheep

BACKGROUND

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.

MATERIALS AND METHODS

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.

RESULTS

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).

CONCLUSION

FDP treatment attenuated significantly the characteristic pulmonary hypertension, lung lymph protein clearance, and pulmonary vascular leakage seen in sheep infused with endotoxin.

Morphine modulates inducible nitric oxide synthase expression and reduces pulmonary oedema induced by α-naphthylthiourea

This study was designed to investigate the possible participation of morphine in pulmonary oedema induced by alpha-naphthylthiourea (ANTU), which is a well-known noxious chemical agent in the lung. Injection of ANTU (15 mg/kg i.p.) produced pulmonary oedema as indicated by an increase in lung weight/body weight ratio and pleural effusion reaching a maximum within 4 h in rat. Administration of morphine prior to ANTU significantly inhibited to pulmonary oedema with a dose-dependent manner. The protective effect of morphine is prevented by peripheral opioid receptor antagonist, naloxone methiodide. ANTU-treated rats were shown positive by inducible nitric oxide synthase immunohistochemical staining. There was no staining in the control group. On the other hand, the degree of staining was markedly reduced in tissue sections by morphine. These results suggest that previous administration of subcutaneous morphine has preventive effect on ANTU-induced pulmonary inflammatory reaction and its effect mediated via peripheral opioid receptors. Application of naloxone with ANTU has no effect on the lung parameters indicating that endogenous opioids do not modulate ANTU-induced damage.

Defective respiratory amiloride-sensitive sodium transport predisposes to pulmonary oedema and delays its resolution in mice

Pulmonary oedema results from an imbalance between the forces driving fluid into the airspace and the biological mechanisms for its removal. In mice lacking the alpha-subunit of the amiloride-sensitive sodium channel (alphaENaC(-/-)), impaired sodium transport-mediated lung liquid clearance at birth results in neonatal death. Transgenic expression of alphaENaC driven by a cytomegalovirus (CMV) promoter (alphaENaC(-/-)Tg+) rescues the lethal pulmonary phenotype, but only partially restores respiratory sodium transport in vitro. To test whether this may also be true in vivo, and to assess the functional consequences of this defect on experimental pulmonary oedema, we measured respiratory transepithelial potential difference (PD) and alveolar fluid clearance (AFC), and quantified pulmonary oedema during experimental acute lung injury in these mice. Both respiratory PD and AFC were roughly 50% lower (P < 0.01) in alphaENaC(-/-)Tg+ than in control mice. This impairment was associated with a significantly larger increase of the wet/dry lung weight ratio in alphaENaC(-/-)Tg+ than in control mice, both after exposure to hyperoxia and thiourea. Moreover, the rate of resolution of thiourea-induced pulmonary oedema was more than three times slower (P < 0.001) in alphaENaC(-/-)Tg+ mice. alphaENaC(-/-)Tg+ mice represent the first model of a constitutively impaired respiratory transepithelial sodium transport, and provide direct evidence that this impairment facilitates pulmonary oedema in conscious freely moving animals. These data in mice strengthen indirect evidence provided by clinical studies, suggesting that defective respiratory transepithelial sodium transport may also facilitate pulmonary oedema in humans.

Bronchiolar expression of aquaporin-3 (AQP3) in rat lung and its dynamics in pulmonary oedema

Aquaporins (AQPs) are water channel proteins that permit osmotically driven water movement. To determine their dynamics in pulmonary oedema, we examined the expression of mRNA and protein for AQP1, AQP3, AQP4, and AQP5 in the lungs of normal and thiourea-treated rats. In the thiourea group, lung water content increased significantly (vs. controls) with the peak at around 4 h. Semi-quantitative RT-PCR showed that AQP3 mRNA in the thiourea group rose significantly, peaking at around 4-8 h. The expression of AQP1, AQP4, AQP5, ENaC and CFTR mRNA each decreased significantly some time after the peak in lung water content. Immunoblot analysis showed that glycosylated AQP3 protein was increased 4-10 h after treatment. Expression of the other AQP proteins was not significantly altered, except for that of AQP4. Immunohistochemical examination revealed that AQP1 was expressed in endothelia, AQP3 in the basal cells of the large airways and in cuboidal cells in the bronchioles, AQP4 in the basolateral membrane of airway cells and AQP5 in type-I pneumocytes. Our results suggest that AQP3 is expressed not only in large airways, but also in bronchioles, and is related to water movement in pulmonary oedema.

Granulocyte colony-stimulating factor enhances alpha-naphthylthiourea-induced pulmonary hypertension

Physiopathological discrepancies exist between the most widely used models of pulmonary hypertension (PH), namely monocrotaline- and hypoxia-induced PH. The development of a new model could help in the understanding of underlying mechanisms. Repeated alpha-naphthylthiourea (ANTU) injections (5 mg/kg weekly, 3 wk) induced pulmonary vascular remodeling, which was associated with development of PH and right ventricular hypertrophy. ANTU followed by granulocyte colony-stimulating factor (G-CSF; 25 microgram. kg(-1). day(-1) subcutaneously, 3 days/wk) induced higher pulmonary arterial pressures and right ventricular hypertrophy than ANTU alone. Lidocaine, which inhibits neutrophil functions, inhibited PH exacerbation by G-CSF. Endothelial nitric oxide synthase expression, measured to assess ANTU-related endothelial toxicity, decreased significantly in ANTU-treated rats and fell even more sharply when G-CSF was given. This occurred despite a significant increase in vascular endothelial cell growth factor expression in lung and right ventricle in rats given ANTU alone and even more in rats given ANTU plus G-CSF. Repeated ANTU administration induces PH with vascular remodeling that can be further aggravated by the neutrophil activator G-CSF.

Thiourea toxicity in mouse C3H/10T1/2 cells expressing human flavin-dependent monooxygenase 3

Human flavin-dependent monooxygenase (FMO) isoforms 1 and 3 were expressed by retroviral gene transfer in mouse C3H/10T1/2 cells. FMO function was determined by the sulfoxidation of p-tolylmethylsulfide (TMS). Enzyme activity ranged from 4 to 30 nmol p-tolylmethylsulfoxide (TMSO)/30 min/mg cell protein for FMO 3 clones; for FMO 1 clones, the range was 1-6 nmol TMSO/30 min/mg. Cytotoxicity in these clones after exposure to thiocarbamate compounds was assessed by clonogenic assay. Thiourea (TU), phenylthiourea (PTU), and alpha-naphthylthiourea (ANTU) were toxic to FMO 3 cells but not to parental and FMO 1 clones; 50% toxicity was attained at 1x10(-4) M TU, 5x10(-6) M PTU, and 1x10(-6) M ANTU. Toxicity was observed after a minimum exposure time of 6 hr. Parental cells were resistant to toxicity for exposure times spanning the entire clonogenic assay period (10 days). Ethylene thiourea (ETU) was not toxic to FMO 3 cells, but preincubation with 1x10(-3) M ETU blocked TU toxicity. Reducing GSH levels by preincubation with 1x10(-5) M buthionine sulfoxime (BSO) increased TU sensitivity in FMO 3 cells from 1x10(-4) to 1x10(-6) M to achieve 50% toxicity. BSO also increased the sensitivity of "low expressor" FMO 3 clones to TU, but did not alter the refractoriness of either parental or FMO 1 expressing cells to TU. N-Acetylcysteine afforded modest protection to TU toxicity by shifting 50% cytotoxicity for TU from 5x10(-5) to 1x10(-3) M. TU mutagenicity was assayed by the development of ouabain resistance in parental and FMO 3 C3H/10T1/2 cells. Exposure to N-methyl-N'-nitro-N-nitrosoguanidine (MNNG, direct acting mutagen) and TU was executed with and without prior sensitization with BSO. The mutation frequency for MNNG was 76/1x10(6) surviving cells, whereas no mutants were observed for TU-exposed cultures. The results of this study show that, in isolation, the major human hepatic form of FMO is capable of promoting thiocarbamate toxicity. Consistent with the known reactivity of thiocarbamate intermediates with GSH, treatments that alter GSH levels also altered toxicity in either the protective or sensitizing direction. These cell lines expressing variable levels of FMO 3 and TU sensitivity should prove useful as in vitro systems for dissecting the thiocarbamate toxicity pathway.

Acute effects of pentobarbital, thiopental and urethane on lung oedema induced by alpha-naphthythiourea (ANTU)

This study was designed to investigate the possible participation of urethane, pentobarbital sodium and thiopental sodium anaesthesia in the lung oedema induced by alpha-naphthylthiourea (ANTU), which is a well known noxious chemical agent in the lung. ANTU when injected intraperitoneally (i.p.) into rats (10 mg x kg (-1) i.p.) produced lung oedema as indicated by an increase in lung weight/body weight (LW/BW) ratio and pleural effusion (PE) reaching a maximum within 4 h. Administration of urethane prior to ANTU, at doses of 100 and 200mg(100g)(-1), elicited a significant and dose-dependent inhibition in LW/BW ratio and PE. Thiopental sodium at doses of 25, 50 mg x kg (-1), also produced a significant and dose-dependent inhibition of both parameters. Prior i.p. injection of pentobarbital sodium at a dose of 40 mg x kg (-1) elicited a significant inhibition in both parameters. These results suggest that i.p. urethane, thiopental sodium and pentobarbital sodium pretreatment have a prophylactic effect on ANTU-induced lung injury in rats. The possible role of the anaesthetics in lung oedema induced by ANTU and the possible underlying mechanisms are discussed.

Role of aquaporins in alveolar fluid clearance in neonatal and adult lung, and in oedema formation following acute lung injury: studies in transgenic aquaporin null mice

Aquaporin (AQP) water channels provide a major pathway for osmotically driven water movement across epithelial and microvascular barriers in the lung. We used mice deficient in each of the three principal lung aquaporins, AQP1, AQP4 and AQP5, to test the hypothesis that aquaporins are important in neonatal lung fluid balance, adult lung fluid clearance and formation of lung oedema after acute lung injury. Wet-to-dry weight ratios (W/D) in lungs from wild-type mice decreased from 7.9 to 5.7 over the first hour after spontaneous delivery. AQP deletion did not significantly affect W/D at 45 min after birth. Alveolar fluid clearance was measured in living ventilated mice in which 0.5 ml saline containing radiolabelled albumin was instilled into the airspaces. Fluid clearance was 17.4 % in 15 min and inhibited >90 % by amiloride, but clearance was not affected by AQP deletion. W/D was measured in established models of acute lung injury - acid aspiration and thiourea administration. Two hours after intratracheal administration of HCl, W/D increased from 3.7 to 7.5 but was not affected by AQP deletion. Three hours after intraperitoneal infusion of thiourea, W/D increased to 5.5 and marked pleural effusions appeared, but there were no differences in wild-type and AQP knockout mice. Hyperoxic subacute lung injury was induced by 95 % oxygen. Neither mean survival (143 h) nor W/D at 65 h (5.1) were significantly affected by AQP deletion. Despite their role in osmotically driven lung water transport, aquaporins are not required for the physiological clearance of lung water in the neonatal or adult lung, or for the accumulation of extravascular lung water in the injured lung.

Pretreatment with cationic lipid-mediated transfer of the Na+K+-ATPase pump in a mouse model in vivo augments resolution of high permeability pulmonary oedema

Resolution of pulmonary oedema is mediated by active absorption of liquid across the alveolar epithelium. A key component of this process is the sodium-potassium ATPase (Na+K+-ATPase) enzyme located on the basolateral surface of epithelial cells and up-regulated during oedema resolution. We hypothesised that lung liquid clearance could be further up-regulated by lipid-mediated transfer and expression of exogenous Na+K+-ATPase cDNA. We demonstrate proof of this principle in a model of high permeability pulmonary oedema induced by intraperitoneal injection of thiourea (2.5 mg/kg) in C57/BL6 mice. Pretreatment of mice (24 h before thiourea) by nasal sniffing of cationic liposome (lipid #67)-DNA complexes encoding the alpha and beta subunits of Na+K+-ATPase (160 microg per mouse), significantly (P<0.01) decreased the wet:dry weight ratios measured 2 h after thiourea injection compared with control animals, pretreated with an equivalent dose of an irrelevant gene. Whole lung Na+K+-ATPase activity was significantly (P<0.05) increased in mice pretreated with Na+K+-ATPase cDNA compared both with untreated control animals as well as animals pretreated with the irrelevant gene. Nested RT-PCR on whole lung homogenates confirmed gene transfer by detection of vector-specific mRNA in three of four mice studied 24 h after gene transfer. This demonstration of a significant reduction in pulmonary oedema following in vivo gene transfer raises the possibility of gene therapy as a novel, localised approach for pulmonary oedema in clinical settings such as ARDS and lung transplantation.

Pleural Disease in the Intensive Care Unit

Pleural disease itself is an unusual cause for admission to the intensive care unit (ICU). Pleural complications of diseases and procedures in the ICU are common, however, and the impact on respiratory physiology is additive to that of the underlying cardiopulmonary disease. Pleural effusion and pneumothorax may be overlooked in the critically ill patient due to alterations in radiologic appearance in the supine patient. The development of a pneumothorax in a patient in the ICU represents a potentially life-threatening situation. This article reviews the etiologies, pathophysiology, and management of pleural effusion, pneumothorax, tension pneumothorax, and bronchopleural fistula in the critically ill patient. In addition, we review the potential complications of thoracentesis and chest tube thoracostomy, including re-expansion pulmonary edema.

Stimulated pulmonary cell hyperplasia underlies resistance to alpha-naphthylthiourea

The rodenticide alpha-naphthylthiourea (ANTU) causes pulmonary edema and pleural effusion that leads to death via pulmonary insufficiency. Rats become resistant to the lethal effect of ANTU if they are first exposed to a small, nonlethal dose of ANTU. Young rats are also resistant to ANTU. The mechanism by which rats develop resistance by a prior, small dose exposure has yet to be determined. Growth factor induced-pulmonary hyperplasia has been demonstrated to attenuate ANTU-induced lung leak. We hypothesized that a small dose of ANTU protects against a large dose through pulmonary cell hyperplasia induced by the protective dose. Furthermore, we hypothesized that this hyperplasia is associated with altered transcription of growth factors. Male Sprague-Dawley rats (175-225 g) were treated with a low dose of ANTU (5 mg ANTU/kg; ANTU(L)) 24 h before challenge with a 100% lethal dose of ANTU (70 mg ANTU/kg; ANTU(H)) resulting in 100% protection against the lethal effect of ANTU(H). ANTU(L) protection against ANTU(H) lasted for 5 days, slowly phased out, all being lost by day 20. Injury was assessed by estimating pulmonary vascular permeability and through histopathological examination. ANTU(H) alone resulted in an increase in pulmonary edema leading to animal death. However, injury was prevented if the rats were first treated with ANTU(L). There was a stimulation of pulmonary cell hyperplasia in the lungs of ANTU(L) treated rats as measured by [3H]-thymidine and bromodeoxyuridine incorporation. Treatment with the antimitotic agent colchicine abolished ANTU(L)-induced resistance to ANTU(H). ANTU resistant rats were also resistant to the lethal effect of paraquat. Paraquat is not taken up by pneumocytes if they are undergoing hyperplasia. ANTU(L) administration resulted in an up regulation of gene transcription for keratinocyte growth factor, transforming growth factor-beta, keratinocyte growth factor receptor and epidermal growth factor receptor as determined through reverse transcription-polymerase chain reaction. A significant increase in transforming growth factor-alpha was not observed. These findings collectively suggest that ANTU(L)-induced pulmonary cell hyperplasia underlies resistance to ANTU(H). Furthermore, the stimulation of hyperplasia may be due to altered growth factor and growth factor receptor expressions.

Rapid reperfusion causes stress failure in ischemic rat lungs

OBJECTIVE

Rapid reperfusion may be injurious to the ischemic lung. Our aim was to confirm that slow reperfusion improves postischemic pulmonary function and to elucidate the ultrastructural changes associated with slow versus rapid reperfusion. METHODS. We used an ex vivo perfused rat lung transplant model to study the effect of slow versus rapid reperfusion on subsequent lung function and morphologic conditional. Functional assessment was performed in (1) fresh lung, slowly reperfused; (2) fresh lung, rapidly reperfused; (3) ischemic lung (4 hours at 22 degrees C), slowly reperfused; and (4) ischemic lung, rapidly reperfused.

RESULTS

In group 4, the shunt fraction (P=.001), airway pressure (P=.001), and wet/dry ratio (P=.01) were significantly higher than in groups 1 through 3. Light and electron microscopy of slowly reperfused ischemic lungs (n=4) appeared normal. Rapidly reperfused ischemic lungs (n=4) demonstrated massive alveolar edema hemorrhage, and epithelial "blebbing" by light microscopy. Electron microscopy identified the blebbing as separation of the epithelial layer from an intact basement membrane by edema fluid. The epithelial layer was disrupted in numerous locations. Complete disruption of all layers of the blood-gas barrier was occasionally present.

CONCLUSION

Rapid reperfusion of the ischemic lung is an important contributing factor to reperfusion lung injury resulting in mechanical stress failure of the alveolar/capillary barrier. Gradual reintroduction of blood flow to the ischemic lung improves oxygenation.

Three-dimensional analysis of vacuoles and surface invaginations of capillary endothelia in the eel rete mirabile

One layer of attenuated endothelia of continuous capillaries provides a partially selective diffusion barrier between the blood and the interstitium. Ultrastructures of membrane specialization without the known physiologic functions have been found in blood vessel endothelia. The vacuolar profiles or vacuole-like, membrane-bound structures, which are larger than plasmalemmal vesicles, have been observed routinely in normal endothelial cytoplasm or in blood vessels challenged by insults in electron microscopic studies. Three-dimensional information from serial sections is required to understand the organization and functions of vacuole-like structures in capillary endothelium. The capillaries in eel retia mirabile were perfused with electron-dense tracers, glutaraldehyde in buffer, and were processed for transmission electron microscopy. Ribbons of serial thin sections without counterstaining were examined under a transmission electron microscope. The vacuolar profiles inside endothelial cytoplasm were investigated with the techniques of serial section analysis and three-dimensional reconstruction from serial sections. The vacuole-like structures inside endothelial cytoplasm either were connected to extracellular (luminal, abluminal) compartments or existed as isolated vacuoles from serial section analysis. In the eight series examined in this study, six of ten vacuole-like structures were classified as isolated vacuoles inside endothelia, and their diameters ranged between 186 nm and 266 nm. Two of ten vacuole-like structures were found to extend to the luminal surface of capillaries as luminal, pocket-like invaginations. One of ten vacuole-like structures was found to be connected to the albuminal compartment, and another one existed as an extracellular compartment surrounded by endothelia. Three-dimensional projection of the vacuolar compartments from serial sections showed that endothelial cytoplasm of sheet shape protruded and folded over adjacent endothelium. Three-dimensional information from serial sections reveals the organization of vacuolar profiles and pocket-like invaginations from the cell surfaces in capillary endothelium. The vacuolar profiles in capillary endothelia in two-dimensional electron photomicrographs may represent the extracellular compartments surrounded by the endothelial finger-like extensions. The results indicate that the luminal and abluminal surfaces of the capillary lumen are not smooth or static, and endothelia may change their shape in three dimensions through cytoplasmic protrusions when the tissue environment changes.

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.

Clara cell protein (CC16) in pleural fluids: a marker of leakage through the visceral pleura

Pleural fluid (PF) proteins either derive from serum by diffusion or are locally secreted within the pleural space. Another hypothetical origin is a leakage of lung secretory proteins across the visceral pleura. To test this hypothesis, we investigated the occurrence, sources, and determinants in PF of CC16, a small-size and readily diffusible protein of 16 kDa secreted by bronchiolar Clara cells. CC16 concentration was determined by a sensitive latex immunoassay in serum and PF of 117 subjects (86 exudates and 31 transudates) and, for purpose of comparison, in ascites samples from another group of 38 subjects (7 exudates and 31 transudates). CC16 was also studied in serum and PF of normal rats and in rats with pleural exudate induced by alpha-naphthyl-thiourea (ANTU). The levels of CC16 in PF and ascites were highly correlated with that in serum, suggesting a diffusional exchange across the pleural/blood and peritoneal/blood barriers. Whereas CC16 occurs at similar levels in ascites and serum, the protein was found to be more concentrated in PF than in serum in both humans (geometric mean in microg/L, 26.2 versus 14.6, p < 0.0001) and rats (213 versus 16.2, p < 0.001). A local synthesis of CC16 appeared unlikely in view of the lack of CC16-immunostaining in pleura of both species. The only plausible explanation for these findings is that CC16 in PF originates from two sources: diffusion from plasma and a leakage from the lung into the pleural space across the semipermeable visceral pleura. This interpretation is supported by a markedly increased leakage of CC16 in experimental exudates induced by ANTU and the finding of high CC16 concentrations in human transudates associated with congestive heart failure, two conditions wherein PF has been shown to arise from the interstitial spaces of the lung.

An unexpected interaction between NG-nitro-L-arginine methyl ester and L-arginine in alpha-naphthylthiourea-induced pulmonary oedema in rats

This study was designed to investigate the possible participation of the L-arginine-nitric oxide (NO) pathway in the lung oedema induced by alpha-naphthylthiourea, which is a well-known noxious chemical agent in the lung. Lung oedema was assessed by measuring fluid accumulation in the pleural cavity and the lung weight/body weight ratio following alpha-naphthylthiourea injection. Administration of NG-nitro-L-arginine methyl ester, a NO synthase inhibitor, prior to alpha-naphthylthiourea, produced a significant inhibition of pleural effusion and lung weight/body weight ratio in a dose-dependent manner. L-Arginine, but not D-arginine, when used higher doses (above 300 mg/kg) prior to alpha-naphthylthiourea injection caused a significant inhibition of pleural effusion without altering lung weight/body weight ratio. Lower doses of L-arginine (below 100 mg/kg) did not elicit an inhibitory effect against alpha-naphthylthiourea-induced pulmonary damage. However, lower doses of L-arginine greatly potentiated the inhibitory effect of NG-nitro-L-arginine-methyl ester against alpha-naphthylthiourea-induced lung oedema when used in combination. The interesting aspect of this study is the inhibition by NG-nitro-L-arginine methyl ester, a NO synthase inhibitor, and L-arginine, an endogenous donor of NO, of the lung oedema induced by alpha-naphthylthiourea. The possible role of the L-arginine-NO pathway in lung oedema induced by alpha-naphthylthiourea and the possible underlying mechanisms are discussed.

Role of the lung in accumulation and metabolism of xenobiotic compounds--implications for chemically induced toxicity

The mammalian lung is exposed to and affected by many airborne and bloodborne foreign compounds. This review summarizes the role of lung in accumulation and metabolism of xenobiotics, some of which are spontaneously reactive or are metabolically activated to toxic intermediates. The specific architectural arrangement of mammalian lung favors that so-called pneumophilic drugs are filtered out of the blood and are retained within the tissue as shown in particular for amphetamine, chlorphentermine, amiodarone, imipramine, chlorpromazine, propranolol, local anaesthetics, and some miscellaneous therapeutics. There is strong evidence that intrapulmonary distribution activity and regulation of drug-metabolizing enzymes in lung is distinct from liver. This review focuses on the metabolic rate of selected compounds in lung such as 5-fluoro-2'-deoxyuridine, local anesthetics, nicotine, benzo(alpha)pyrene, ipomeanol, 4-methylnitrosamino-1-(3-pyridyl)-1-butanone. It is widely accepted that the formation of radical species is a key event in the pneumotoxic mechanisms induced by bleomycin, paraquat, 3-methylindole, butylhydroxytoluene, or nitrofurantoin. Finally, methodological approaches to assess the capacity of lung to eliminate foreign compounds as well as biochemical features of the pulmonary tissue are evaluated briefly.

Biochemical and morphological alterations in xylazine-induced pulmonary edema

Sprague-Dawley rats were given 42 mg/kg xylazine intramuscularly, and lungs were lavaged with phosphate-buffered saline 3, 6, and 12 hr later. Total protein, lactate dehydrogenase (LDH), xanthine oxidase (XO), tumor necrosis factor (TNF), and interleukin 1 (IL-1) were measured in bronchoalveolar lavage fluid (BALF). Protein concentration, LDH, XO, and TNF levels were increased (p < 0.05) in the BALF from xylazine-treated rats as compared to controls. IL-1 level was unchanged at 3 and 6 hr and was reduced (p < 0.05) at 12 hr. Another group of rats was given 42 mg/kg xylazine intramuscularly, and lungs were fixed 0.5 and 12 hr later. Histologically, severe pulmonary edema (PE) involving the alveoli and perivascular stroma was observed. Fibrin, increased numbers of eosinophils, and macrophages with foamy cytoplasm were present in the alveoli of all treated animals. Ultrastructurally, endothelial damage, characterized by thinning, detachment from basement membranes, or bleb formation, was observed. The lesions were similar in both xylazine groups, differing mainly in severity with the 12-hr group having more severe lesions than the 0.5-hr group. To determine whether endothelial injury is caused by direct toxicity of xylazine, bovine pulmonary artery endothelial cells (BPAECs) were incubated with xylazine (0.3, 3, and 30 micrograms) for 0.5 or 3 hr. Xylazine did not have any effects on BPAECs, as indicated by phase-contrast microscopy and dye-exclusion viability assay. These results indicate that xylazine-induced PE is due to increased permeability resulting from endothelial injury, which is not caused by direct effect of xylazine on pulmonary endothelium. While oxygen radicals and TNF are possibly involved, IL-1 does not appear to play a role in xylazine-induced PE.

Experimental hydrostatic pulmonary edema in rabbit lungs. Barrier lesions

In excised rabbit lungs perfused with a 6% albumin solution, hydrostatic pulmonary edema was induced by moderate (about 14 mm Hg) and high increases (about 29 mm Hg) of capillary transmural pressure. Thereafter, lung tissue and proteinaceous edema fluid were fixed by vascular perfusion and analyzed by electron microscopy for possible lesions of the blood-gas barrier. The following observations appear noteworthy: (1) There were distinct and numerous lesions of the epithelial cell layer. In high-pressure edema, frank disruptions on the thin and thick sides of the blood-gas barrier were prominent. In moderate pressure edema epithelial blebs were more conspicuous. (2) In contrast, endothelial lesions were rare in both high- and moderate-pressure experiments. (3) Epithelial Type I cells revealed an enormous plasticity as illustrated by the formation of large epithelial blebs. (4) Although the entire microvasculature was subjected to high pressures, barrier lesions were exclusively seen in regions with alveolar edema. These findings suggest that barrier leaks play a role in both hydrostatic and permeability lung edema and that the differences between both types of edema rather reflects the type and extent of injury to the alveolar epithelial barrier and the associated inflammatory reaction.

Effects of thiourea tolerance on plasma histamine, and lung vascular permeability

Adult male rats treated with a lethal edematogenic dose of thiourea (TU) (10.0 mg/kg, intraperitoneally) responded with significant elevations in plasma histamine, lung vascular permeability and 100% mortality over a subsequent 24-h period. When rats were pretreated with a small non-lethal dose of TU (0.5 mg/kg) and subsequently challenged with the lethal dose at 1, 4, 8, 16 and 32 days later, there was complete protection against death for at least 8 days and partial protection for an additional 24 days. This decrease in mortality correlated quite closely with reduced plasma histamine levels and diminished pulmonary vascular permeability. The results suggest that reduced exposure of the pulmonary vasculature to histamine may offer a partial explanation for tolerance to thiocarbamide compounds in the rat.

Protection of rats against the effects of alpha-naphthylthiourea (ANTU) by elevation of non-protein sulphydryl levels

We have investigated the influence of the elevation of pulmonary glutathione (GSH) levels on the toxicity of the rodenticide alpha-naphthylthiourea (ANTU) to rat lung. Administration of phorone (diisopropylidene acetone; 200 mg/kg i.p.) caused an initial depletion of both pulmonary and hepatic GSH followed after 48 hr by a marked elevation in both tissues, due most probably to a compensatory rebound synthesis. In control rats, ANTU produced a dose-dependent lethality, hydrothorax and loss of ability of lung tissue to accumulate adenosine and spermidine (markers of endothelial and epithelial cell function, respectively). These effects were prevented or markedly ameliorated when ANTU was given 48 hr after pretreatment with phorone. The mechanism of the protection by phorone pretreatment against ANTU-induced pulmonary toxicity is unclear. It may be due, in part, to elevated GSH levels in pulmonary endothelial cells and, in addition, to increased detoxification of ANTU in the liver, resulting in a decreased availability to the lung.

Effects of thiourea on pulmonary vascular permeability and on lung and plasma histamine levels in rats

The intraperitoneal administration of thiourea (TU) to mature male rats results in a significant increase in lung vascular permeability to Evans Blue dye (EBD). On the other hand, young, sexually immature rats are resistant to this effect. The increase in lung vascular permeability in response to TU in mature rats is associated with corresponding increases in lung and plasma histamine levels. The correlation of increases in lung and plasma histamine in response to TU is similar to that reported for ammonium salts which produce similar pulmonary edema.

gamma-Glutamyltranspeptidase in rat bronchoalveolar lavage fluid as a probe of 4-ipomeanol and alpha-naphthylthiourea-induced pneumotoxicity

Bronchoalveolar lavage fluid analysis has gained popularity as a rapid in vivo screen to evaluate the toxicity of both systemic and inhaled pneumotoxicants and is used in addition to the more commonly evaluated pathologic changes. This study evaluated gamma-glutamyltranspeptidase (GGT) in the bronchoalveolar lavage fluid (BALF) along with the more commonly measured enzyme, lactate dehydrogenase (LDH), as a useful indicator of acute lung injury from systematically administered pneumotoxicants. Adult male rats were injected ip with 2, 3, or 3.5 mg/kg body weight of alpha-naphthylthiourea (ANTU) or 5, 10, or 20 mg/kg of 4-ipomeanol, and measurements were made 8 or 24 hr postdose, respectively. ANTU, which selectively damages pulmonary endothelial cells, caused extensive pleural effusions with striking increases in BALF protein and white blood cell (WBC) content. 4-Ipomeanol, which selectively damages nonciliated bronchiolar Clara cells, caused dose dependent increases in both GGT and LDH activities in the BALF with GGT being increased at all doses tested. BALF protein content was also increased in the 4-ipomeanol-treated groups, but this change was not dose dependent. Analysis of GGT in BALF was a sensitive method to assess cytotoxicity associated with 4-ipomeanol-induced injury but was less useful in monitoring pulmonary endothelial cell damage induced by ANTU. Measurements of BALF protein and WBC content proved to be better in assessing injury by agents such as ANTU that primarily affect vascular permeability.

Relationship of pleural effusions to increased permeability pulmonary edema in anesthetized sheep

We studied anesthetized sheep to determine the relationship between increased permeability pulmonary edema and the development and mechanism of pleural effusion formation. In 12 sheep with intact, closed thoraces, we studied the time course of pleural liquid formation after 0.12 ml/kg i.v. oleic acid. After 1 h, there were no pleural effusions, even though extravascular lung water increased 50% to 6.0 +/- 0.7 g/g dry lung. By 3 h pleural effusions had formed, they reached a maximum at 5 h (48.5 +/- 16.9 ml/thorax), and at 8 h there was no additional accumulation of pleural liquid (45.5 +/- 16.9 ml). Morphologic studies by light and electron microscopy demonstrated subpleural edema but no detectable injury to the visceral pleura, suggesting that the pleural liquid originated from the lung and not the pleura. In nine sheep, we quantified the rate of formation of pleural liquid by enclosing one lung in a plastic bag. By comparing in the same sheep the volume of pleural liquid collected from the enclosed lung to the volume found in the opposite intact chest, we estimated the rate of liquid absorption from the intact chest to be 0.32 ml/(kg.h); we had previously reported a liquid absorption rate of 0.28 ml/(kg.h) in normal sheep. These studies also supported the conclusion that the majority of the pleural liquid originated from the lung because we could account for all of the pleural liquid that was formed and cleared. The volume of pleural liquid collected from the enclosed lungs was equal to 21% of the excess lung liquid that formed after oleic acid-induced lung injury. Thus, the pleural space and parietal pleural lymphatic pathways are important pathways for the clearance of pulmonary edema liquid after experimentally induced increased permeability pulmonary edema.

Effect of acute lung injury on metabolism of adenine nucleotides in rat perfused lung

1. The hydrolysis of adenosine di- and monophosphate (ADP, AMP) was studied in perfused lungs isolated from rats treated with alpha-naphthylthiourea (ANTU) to induce acute lung injury. This injury is associated with damage to the endothelium, the locus of the ADP and AMP hydrolysing enzymes. 2. Treatment with ANTU did not change the proportion of [3H]-ADP surviving a single passage through the pulmonary circulation, at any time up to 50 h after ANTU. Less than 8% and 2% respectively of 1 or 0.1 mumol ADP, given as a bolus, appeared in lung effluent. 3. The metabolites of ADP, AMP and adenosine in lung effluent were increased fro 2 h after ANTU. 4. Metabolism of [3H]-AMP as substrate was always low but, following ANTU treatment, the adenosine content of lung effluent increased four fold. 5. It appears that, in spite of considerable endothelial cell damage, as demonstrated by pulmonary oedema, the ectoenzymes catalysing ADP and AMP hydrolysis were relatively little affected by ANTU.

Pulmonary endothelial and alveolar epithelial lesions induced by O,O,S-trimethyl phosphorothioate in rats

The morphogenesis of pulmonary injury induced by an impurity present in a commercially important organophosphorus insecticide, O,O,S-trimethyl phosphorothioate (OOS-TMP), was studied by combined light and transmission electron microscopy. Weanling female WAG/Rij rats received OOS-TMP dissolved in corn oil by gavage and were studied at intervals from 6 to 168 h after treatment. Sequestration of neutrophils was initially observed at 12 h after treatment and was accompanied by interstitial oedema. Plasmalemma alterations in endothelium lining capillaries and small arteries and veins were observed from 12 to 120 h after treatment and were accompanied by endothelial cell detachment and separation from the basal lamina. Abundant aggregates of fibrin were sequentially observed in intravascular, interstitial, and alveolar spaces. Platelet aggregation and degranulation were occasionally observed in capillaries as early as 12 h after treatment, and frequently observed in capillaries and small vessels from 24 to 96 h after treatment. Significant increases in wet lung weight and lung water content occurred at the same time that morphologic changes were observed in pulmonary endothelium. Alterations in type I alveolar epithelial cells were initially observed at 24 h after treatment. Cell swelling, fragmentation, and necrosis were observed in both type I and type II cells and resulted in a bare basal lamina. Marked attenuation, hypertrophy, and proliferation of type II epithelial cells followed alveolar epithelial cell injury and loss. Minimal changes were observed in non-ciliated bronchiolar epithelial (Clara) cells; predominant changes included the loss of surface microvilli and apical cytoplasmic bulge. The results of this study indicate that the endothelium and alveolar epithelium are the predominant cell types in the rat lung injured following OOS-TMP administration.(ABSTRACT TRUNCATED AT 250 WORDS)

Structural heterogeneity within the pulmonary microcirculation of the normal rat

Extra-alveolar microvessels of the rat were described previously as nonmuscular, partially muscular, and muscular (Hislop and Reid, 1978). Based on these structural criteria, the present morphometric results present evidence that mean thickness of the endothelium was significantly greater in the muscular microvessels than in each of the other microvessel categories. The percentage of endothelial surface occupied by attenuated segments (20-30 nm maximal thickness) was greatest in the nonmuscular and partially muscular microvessels. Mean plasmalemmal vesicle diameters were consistent throughout the microvascular units. Vesicle numerical densities, however, were significantly greater in the alveolar capillary endothelium than in endothelia of the nonmuscular, partially muscular, and muscular microvessels. Endothelial vacuoles (diameters greater than 150 nm) were not observed in either the capillaries or the nonmuscular microvessels. Mean diameters and numerical densities of vacuoles observed in endothelia of the partially muscular and muscular microvessels were, however, statistically similar. Subclassification of the partially muscular and muscular microvessels by ultrastructural characteristics as arterioles or venules (Rhodin, 1978; Michel, 1982) served to identify greater numerical densities of vesicles in the endothelium of venules than that of the arterioles. As expected, mean thicknesses of the periendothelial connective tissue spaces varied directly with the relative muscularity of the respective microvessels. Based upon the morphometric data presented in this study, future investigations of pulmonary microvascular functions should include considerations of the observed regional variations of endothelial cell ultrastructure.

Lavage angiotensin-converting enzyme as a marker of lung injury

The source of angiotensin-converting enzyme (ACE) in lavage fluid remains controversial. I reassessed the levels of ACE in lavage fluid in contrasting models of lung injury in rats. In all 3 models examined, there was at least a 3-fold elevation in both ACE activity and total protein levels. However, determination of enzyme activity relative to total protein content (enzyme specific activity) revealed contrasting patterns. High dose intratracheal bleomycin instillation (500 micrograms) induced an increase in ACE activity relative to total protein. When a lower dose of bleomycin (50 micrograms) or when a 30-h exposure to 100% oxygen were used, both ACE and protein increased but enzyme specific activity did not change. In contrast, exposure to 100% oxygen for 48 h or to alpha-naphthylthiourea, an agent that rapidly induces protein edema without cell injury, caused a decrease in enzyme specific activity. The enzyme found in lavage fluid in these models is identical to the lung tissue enzyme with respect to cofactor requirements, inhibition by captopril, and has an apparent molecular weight of 175 kDa by SDS-polyacrylamide gel electrophoresis. These studies clearly refute the null hypothesis that lavage ACE levels in the injured lung merely reflect altered bulk protein transmigration.

Effects of pulmonary oedema on pharmacokinetics of adenosine in rat isolated lungs

1 Pulmonary oedema, assessed by decreases in the lung dry weight:wet weight ratio, was induced in rats by a single i.p. injection of alpha-naphthylthiourea (ANTU). The oedema reached a peak at 4 h after ANTU and had completely resolved after 28 h. 2 Pulmonary pharmacokinetics of adenosine were measured in isolated, perfused lungs using radiolabelled adenosine and sucrose, injected into the perfusate as a single bolus. 3 By 1 h after ANTU the 1 min efflux of tracer for adenosine increased to over 60% and remained high until 16 h after ANTU. The time for 50% of injected radioactivity to appear in lung effluent (t1/2) for adenosine was reduced from its normal value of greater than 120 s to a minimum of 27 s at 1 h after ANTU. The proportion of adenosine in lung effluent did not change until 16 h after ANTU treatment but returned to normal by 50 h. 4 There were only minimal changes in the T1/2 and 1 min efflux for sucrose following ANTU treatment. 5 It appears that both the uptake and metabolism of adenosine are affected by ANTU-induced lung damage. The early effects are chiefly on uptake with metabolism remaining normal. Later (after 16 h) metabolism is decreased with uptake recovering to normal levels. 6 The effects on adenosine uptake paralleled the development and the resolution of oedema, suggesting that this variable might provide a biochemical index of the physical processes leading to lung oedema.

Microvascular leakage to platelet activating factor in guinea-pig trachea and bronchi

Conscious guinea-pigs received platelet activating factor (PAF, 0.03-0.25 microgram/kg, i.v.) and colloidal carbon (C, tracer for microvascular leakage). Fifteen min later the animal was killed and C-labelled microvessels (leakage) were detected in the mucosal/submucosal region of tracheal and bronchial sections. PAF was more potent than LTD4 or histamine. The numbers of leaky vessel were dose-related, arterioles and arteries were not affected, leaky vessels were seen from proximal trachea to intrapulmonary bronchi and carbon was not apparent in the alveolar wall. The effect was quick in onset, of short duration, could be repeated, was not produced by lyso-PAF and was unaffected by thrombocytopaenia (produced by an antiserum). Thrombocytopaenia itself did not cause leaky vessels in the airways nor affect histamine responses. Thus, PAF causes an increase in microvascular leakage in the conducting airways, which is not dependent on platelets. The affected vessels are probably postcapillary bronchial venules and PAF may act via an endothelial cell receptor in these microvessels. This leakage effect of PAF in the airways could contribute to features of bronchial asthma.

A histological method for studying the effects of drugs on mediator-induced airway microvascular leakage in rodents

Methods are described for studying the effects of drugs on increases in tracheobronchial microvascular permeability (leakage) induced by inflammatory mediators. A model in conscious guinea pigs (in which the leakage effects resulted from circulating mediator) and a model in anesthetized rats (in which the leakage effects resulted from application of the mediator to the airway lumen) are described. Inhibitor drugs were given i.v. 2 min before the mediator. In guinea pigs either histamine or leukotriene D4 (LTD4) and colloidal carbon (C, the tracer molecule for leakage) were administered together iv.; in rats 5-hydroxytryptamine (5-HT, 100 micrograms) was injected intratracheally followed by i.v. colloidal carbon. Tracheal and bronchial tissues were removed 15 min later from the killed animals and prepared for histology, and the number of C-labeled microvessels in the mucosal/submucosal region of 7-micron sections was counted. In guinea pigs, leakage produced by LTD4 or histamine was related to the dose administered and the relative potency of LTD4:histamine was approximately 123:1, on a molar basis. Leakage caused by histamine, but not by LTD4, was prevented by mepyramine (1 mg/kg) and LTD4-induced leakage was prevented by FPL 55712 (1 mg/kg). Terbutaline (1 mg/kg) attenuated leakage to both mediators but never abolished it. In rats, leakage was also seen to 5-HT, which was prevented by methysergide (1 mg/kg) and markedly attenuated by ketanserin (1 mg/kg) or by terbutaline (1 mg/kg). It is suggested that the colloidal carbon tracer technique has application to pharmacological studies designed to examine the effects of drugs on mediator-induced permeability to macromolecules in the tracheobronchial microcirculation.

Vascular tracers alter hemodynamics and airway pressure in anesthetized sheep

The technique of vascular labeling was developed to mark sites of increased microvascular permeability. We used the vascular labeling technique in anesthetized sheep and found that hemodynamics and airway pressure were adversely affected by intraarterial infusions of two vascular tracers. Monastral blue (nine sheep) immediately caused systemic arterial hypotension, pulmonary arterial hypertension, and bronchoconstriction. All three physiological responses were partially blocked by a cyclooxygenase inhibitor (indomethacin) but not by an H1-antihistamine (chlorpheniramine). Colloidal gold (nine sheep) caused immediate, but less dramatic, pulmonary arterial hypertension which was not attenuated by the blocking agents. We conclude that these two vascular tracers caused detrimental physiological side effects in sheep at the usual doses used to label injured microvessels in other species.

The effect of alphanapthylthiourea (ANTU)-induced acute injury on lung binding of antibody to angiotensin converting enzyme (ACE)

The effects of ANTU-induced acute pulmonary capillary injury on lung and serum ACE functional activity and the specific accumulation of radio-labelled anti-ACE in lung were explored. Rats were injected either with ANTU or the solvent and sacrificed at various intervals up to one week after injection. All ANTU-injected animals developed pulmonary edema and bilateral pleural effusions which resolved by the one week time point. At no time was there any significant change in serum ACE levels. The specific activity of total lung ACE however rose from 11.0 +/- .95 (mean +/- SEM) to 18.4 +/- 1.1 by two hours after ANTU; by 24 hours, however, solubilized lung ACE had fallen significantly to 6.9 +/- .79 (p less than .01). Total lung ACE had returned to control values by one week. In parallel groups of animals the accumulation of 125I-labelled anti-ACE (AA) or normal sheep immunoglobulin (NSG) was compared in control and ANTU-treated rats. The ratio of the radioactivity in the lungs of AA--injected animals to that in NSG--injected animals fell significantly after ANTU administration (5.0 +/- .88 to 1.2 +/- .28 at 2 hours) suggesting that immunoreactive ACE had fallen despite an increase in ACE functional activity. The decreased binding of AA at the early time points perhaps reflects internalization of endothelial cell ACE in response to injury and an inability of the antibody to interact with the enzyme. The reduction in binding at 24 hours (1.38 +/- .47) correlates with a reduction in total lung ACE. ANTI-ACE may be a useful reagent for quantitating endothelial cell damage following lung injury.

Oxidant gas injury to the lung: a discussion on the functional implications

Acute toxic inhalation by the oxidant gases, particularly ozone (O3), nitrogen dioxide (NO2) and oxygen (O2) at high tension, has been assumed to be no more than a chemical burn of the epithelial surface. More recently, oxidant toxic inhalation has been appreciated as a complex process involving biochemical, morphological and functional changes which are qualitatively similar although inducible by different agents. Recent advances in pulmonary pathophysiology, inhalation toxicology and particularly endothelial biology now challenge the validity of a theoretical framework which seemed almost complete just 5 years ago. Considerable attention has been paid in recent years to the biochemical events occurring at the moment of and immediately following exposure to the oxidant gases. Progress in elucidating the initial events has been rapid and promises a more complete picture in the near future. Studies of the pathophysiologic mechanisms associated with toxic inhalation by the oxidant gases have been relatively static, however. In this discussion, implications of recent findings in related fields were examined in an effort to identify new hypotheses and directions for investigation.