Effects of topical platelet activating factor on the guinea-pig tracheobronchial mucosa in vivo

Platelet activating factor (PAF) has been reported to produce a variety of airway effects including epithelial damage and increased airway-lung absorption of hydrophilic tracers. The present study examines effects of PAF on the guinea-pig tracheobronchial mucosa in vivo. Vehicle with and without PAF (4.0 and 8.0 nmol) was superfused onto the tracheobronchial mucosa. The levels of ¹²⁵I-albumin, previously given intravenously, were determined in tracheobronchial lavage fluids as an index of mucosal exudation of plasma. The mucosa was also examined by scanning electron microscopy. In separate animals, ^99mTc-DTPA (a low molecular weight, 492 Da, hydrophilic tracer) was superfused onto the mucosal surface through an oro-tracheal catheter, together with vehicle or PAF (8.0 nmol). A gamma camera determined the disappearance rate of ^99mTc-DTPA from the airways as an index of mucosal absorption. PAF produced dose-dependent mucosal exudation of plasma up to 20-fold greater than control (P < 0.001). However, PAF did not damage the epithelium and the absorption ability of the airway mucosa was unaffected. The results, in contrast to previous reports, suggest that PAF may not readily damage the airway mucosa even at large exudative doses of the agent. The present finding support the view that the plasticity of the epithelial junctions allows the creation of valve-like paracellular pathways for unidirectional clearance of extravasated plasma into the airway lumen. We suggest that endogenous PAF may participate in first line respiratory defence reactions by causing lumenal entry of bulk plasma without harming the epithelium.     

Effects of hydrogen peroxide on the guinea-pig tracheobronchial mucosa in vivo.

Lumenal entry of plasma (mucosal exudation) is a key feature of airway inflammation. In airways challenged with histamine-type mediators and allergen the mucosal exudation response occurs without causing epithelial derangement and without increased airway absorption. In contrast, reactive oxygen metabolites may cause mucosal damage. In this study, involving guinea-pig airways, we have examined effects of H2O2 on airway exudation and absorption in vivo. Vehicle or H2O2 (0.1 and 0.5 M) was superfused onto the tracheobronchial mucosal surface through an oro-tracheal catheter. 125I-albumin, given intravenously, was determined in tracheobronchial tissue and in lavage fluids 10 min after challenge as an index of mucosal exudation of plasma. The tracheobronchial mucosa was also examined by scanning electron microscopy. In separate animals, 99mTc-DTPA was superfused 20 min after vehicle or H2O2 (0.1 and 0.5 M) had been given. A gamma camera determined the disappearance rate of 99mTc-DTPA from the airways as an index of airway absorption. The high dose of H2O2 (0.5 M) produced epithelial damage, increased the absorption of 99mTc-DTPA (P < 0.001), and increased the exudation of plasma (P < 0.001). Notably, it appeared that all extravasated plasma had entered the airway lumen within 10 min. These data demonstrate that H2O2 differs from exudative autacoids such as histamine by causing both epithelial damage and plasma exudation responses. These data also agree with the view that the epithelial lining determines the rate of absorption and is responsible for the valve-like function that allows lumenal entry of extravasated bulk plasma without any increased inward perviousness.     

Allergen, bradykinin, and capsaicin increase outward but not inward macromolecular permeability of guinea-pig tracheobronchial mucosa

When inflammatory stimuli are applied on the airway mucosa, plasma is promptly extravasated from the subepithelial microvessels. The plasma exudate distributes in the lamina propria and much of it is soon transmitted across the epithelial lining. The rapid luminal entry of large plasma solutes must reflect a dramatic change in mucosal permeability. Previously it has been thought that such a perviousness of the mucosal barrier would be bidirectional in nature. This study in anaesthetized guinea-pigs examines whether absorption across the mucosa is increased (above control) during, and immediately after, the plasma exudation process. An oral catheter, introduced into the tracheal lumen, was used to superfuse the lower airways with 0.04 ml of a solution containing the absorption tracer 131I-albumin and a selected dose of a provocating agent: allergen, 3 pmol (ovalbumin in IgE-sensitized animals); bradykinin, 5 nmol; capsaicin, 0.4 nmol; or carbachol, 8 nmol. The superfusate had a desired distribution on the tracheobronchial mucosa so that specific airway and not bronchoalveolar exudation:absorption ratios could be determined. In separate experiments it was confirmed that the present provocations, except carbachol (P greater than 0.05), moved significant amounts of plasma into the airway lumen (P less than 0.001). This was distinctly an increase in the outward mucosal permeability because the absorption of luminal 131I-albumin into circulating plasma was not significantly different from control with any of the provocations (P greater than 0.05). The present data support our notion that unfiltered plasma exudates can operate on the mucosal surface, in first-line defence reactions, without compromising the integrity of the epithelial lining as a barrier to luminal material.(ABSTRACT TRUNCATED AT 250 WORDS)     

Effects of airway luminal concentration of albumin on histamine-induced mucosal exudation of radio-iodine labelled albumin

In an in vivo study of guinea-pig airway barriers we have examined the effects of the luminal concentration of albumin on exudation (outward) and absorption (inward) permeabilities to radio-iodine labelled albumin. Previously validated techniques for superfusion of solutes onto the tracheobronchial mucosal surface and for subsequent tracheal lavage were employed. [125I]albumin was administered intravenously as plasma tracer and [131I]albumin was superfused topically as absorption tracer. Histamine (5.0 nmol) was superfused onto the mucosal surface together with the absorption tracer and in the presence of different albumin concentrations (0.3, 3.0 and 30 mg ml-1). The experiment was terminated 10 minutes after the tracheal mucosal superfusion and samples of plasma and tracheal lavage fluid were collected. The mucosal exudation response was calculated from the detection of [125I]albumin in the airway lumen. The absorption ability of the mucosa was determined by the detection of [131I]albumin in circulating plasma. Histamine induced a significant mucosal exudation of [125I]albumin. This effect was unaffected by the level of albumin on the mucosal surface. There was a small but significant absorption of [131I]albumin in the presence of 0.3 and 3.0 mg ml-1 of albumin in the luminal liquid. An albumin concentration of 30 mg ml-1 markedly increased the rate of absorption of [131I]albumin. However, the absorption rate was not affected by the histamine-induced mucosal exudation process at any level of luminal albumin. The present data further demonstrates that plasma exudation and mucosal absorption are independent processes. The data are in keeping with the view that an increased subepithelial hydrostatic pressure moves the plasma exudate across the mucosa as a distinct outward process.     

Plasma exudation as a first line respiratory mucosal defence

A great variety of provocations of the airway mucosa produce extravasation of plasma from the abundant subepithelial microvessels. A plasma exudate has important actions through its volume, its specific and unspecific binding proteins, its enzyme systems, and its potent peptides (of kinin, complement, coagulation, fibrinolysis and other systems). If allowed to operate on the surface of an intact mucosa the plasma exudate would have important roles in normal airway defence. Recent observations in guinea-pig tracheobronchial airways and in human nasal airways suggest that the mucosal exudation of plasma into the airway lumen is a non-injurious fully reversible process. Threshold exudative responses thus resulted in the appearance of an 'unfiltered' plasma exudate not only in the lamina propria but also on the surface of an undisrupted mucosa. Even after extensive luminal entry of exudate the epithelial lining was intact, as judged by light, fluorescence and electron microscopy. Hence, the epithelial barrier was reversibly permeable when approached from beneath by the plasma exudate. This was a distinct increase in outward permeability, because even during the exudation of plasma the mucosa remained a barrier to luminal solutes. It is possible that the exudate itself, by a slight compressive action on the basolateral aspect of epithelial cells, creates intercellular pathways for its entry into the lumen. Contrary to current beliefs, we propose that plasma exudation should be considered a first line respiratory defence mechanism operating together with other systems of the mucosal surface.     

Epithelial pathways for luminal entry of bulk plasma

Inflammatory challenges of the airway mucosa cause luminal entry of bulk plasma. Extravasation of plasma is well described but the routes for epithelial passage of plasma are largely unknown. Using colloidal gold (5 nm) as tracer we have now examined the fate of extravasated plasma in the airways. The tracer was given intravenously to anaesthetized, ovalbumin-sensitized guinea-pigs 2min prior to airway mucosal challenge with 12pmol ovalbumin (the dose was selected from a separate dose-response study). Tissue specimens were collected 30s, 3 and 6 min after end of challenge (separate time course experiments suggested that the peak rate of entry of plasma occurred at about 5 min). The colloidal gold particles were visualized by autometallographic silver intensification. The gold produced no circulatory disturbance and had a uniform vascular distribution with negligible adherence to vascular endothelium. After challenge gold was first widely distributed in the lamina propria. At 3 and 6 min the tracer was also in the epithelium and airway lumen. It appeared that plasma was moved distinctly between and all around each epithelial cell. Bright field-, scanning-, and transmission electron-microscopy indicated that the luminal entry of plasma did not affect the integrity of the epithelial lining. This study demonstrates that the plasma exudate moves across an intact epithelial layer through ubiquitous paracellular pathways. Even at a pronounced acute plasma exudation response exceedingly small amounts of plasma may pass around a single cell explaining the non-injurious nature of mucosal exudation of bulk plasma in health and disease.     

Topical nitroprusside may reduce histamine-induced plasma exudation in human nasal airways

Mucosal exudation of nonsieved bulk plasma is a key feature of airway defense and inflammation. We have previously observed in guinea pig tracheobronchial airways that endogenous nitric oxide (NO) of the mucosa may tonically suppress the permeability of the subepithelial microcirculation, and that topical administration of the NO donor nitroprusside may reduce plasma exudation responses. The present study examines whether nitroprusside affects histamine-induced mucosal exudation of plasma in the human nasal airway. In a dose-finding tolerability experiment, using changes in nasal patency as response, placebo and nitroprusside (1.2 and 3.6 mg per nasal cavity) were applied on the mucosal surface with a nasal-spray device. Nasal peak expiratory flow (PEF) rates were measured before the application and thereafter every third minute for 15 min. Nitroprusside produced a dose-dependent decrease in nasal PEF rates compared to placebo. Placebo or nitroprusside (7.2 mg) was then given to the right nasal cavity, followed 3 min later by challenge with saline or histamine (600 μg). The drug and the challenge were both applied with a nasal-spray device. With a nasal pool-device, the same large part of the nasal mucosal surface was lavaged before and after the treatment/challenge. The lavage fluid levels of a2-macroglobulin were measured as an index of mucosal exudation of bulk plasma. The histamine-induced lavage fluid level of aj-macroglobulin was significantly higher after treatment with placebo than with nitroprusside. The present data indicate that nitroprusside may have antiexudative effects in human airways. Hence, unlike other microvascular permeability active agents, this pharmacologic principle may be active in both guinea pig and human airways.     

Toluene diisocyanate produces an increase in airway tone that outlasts the inflammatory exudation phase

Toluene diisocyanate (TDI) is a causative agent in occupational asthma. Through an oral catheter TDI, 0.03 microliters, dissolved in 0.02 ml olive oil, was superfused on the tracheobronchial mucosa of anaesthetized guinea-pigs. TDI induced plasma exudation into both airway tissue and lumen (peak effect: 5 hr; duration approximately 17 hr). Light microscopy examinations demonstrated that the epithelium was not disrupted by this process (and that microvessels are abundant just beneath the epithelium). At days 6 and 21 after exposure to TDI PAS-positive cells were increased, but no other histological alterations were found. Also, the occurrence of peptide-containing nerve fibres was not altered by TDI. After TDI-exposure the airway smooth muscle tone was elevated as examined in vitro at base-line and at concentration-response to carbachol. The largest increases in tone were recorded 21 days after exposure to TDI. The abnormally large tone was not associated with an increased thickness of the smooth muscle layer nor was it associated with reduced effects of either beta 2-agonist (terbutaline) or xanthine- (theophylline) relaxants. It is concluded that TDI-induced plasma exudation into guinea-pig airways occurs for 17 hr without disrupting the epithelial lining and without causing major changes in the airway peptidergic innervation. Both the airway tone, and the number of mucous cells, are increased for at least 3 weeks after exposure to TDI.     

Exudative hyperresponsiveness of the airway microcirculation in seasonal allergic rhinitis

Background Mucosal exudation of plasma is a non-injurious, physiological response of the airway microcirculation to different inflammatory processes. The exudative response is similar in the nose and bronchi and exudation occurs in both allergic asthma and rhinitis. The educative response is a specific end-organ function of the mucosal microcirculation that may be altered in airway diseases. Objective This study examines the hypothesis of altered responsiveness of the superficial airway microcirculation to vascular permeability-increasing challenges in sustained allergic inflammation. Methods Fourteen patients with birch-pollen induced allergic rhinitis were studied for 7 weeks during a Swedish birch-pollen season. Nasal symptoms (itching, sneezing. blockage, and discharge) were recorded and the occurrence of pollen was determined. The plasma exudation response was examined by topical histamine challenges at the end (May) and well out of (December) the season. Challenge and lavage were carried out concomitantly using a‘nasal pool’ -device. The unilateral nasal cavity was filled for consecutive 10 minute periods with saline and two concentrations of histamine (80μg/ mL and 400μg/mL). The lavage fluid levels of different-sized plasma proteins (albumin-66 000 D. fibrinogen-340000 D, and α₂-macroglobulin-725000D) were determined. Results The pollen season was mild resulting in only minor nasal symptoms. Histamine produced exudation of all plasma proteins across the microvascular epithelial barriers with particularly strong correlation between the levels of albumin and α₂-macroglobulin (r =0.98; P< 0.001). The exudative response to histamine was concentration-dependent (P<0.05) and, furthermore, it was significantly greater late into the season compared with outside the pollen season (albumin: P < 0.05. tibrinogen: P<0.05. α₂-macroglobulin: P<0.01). Conclusion We conclude that histamine produced concentration-dependent nasal airway exudation of bulk plasma in subjects with seasonal rhinitis and that this response is abnormally great during the pollen season. Whether angiogenesis or increased responsiveness of the mierovascular endothelium may explain this phenomenon now remains unknown. We suggest that a mierovascular exudative hyperresponsiveness may characterize allergic airway disease.     

Mucosal exudation of plasma is a noninjurious intestinal defense mechanism

We have demonstrated in sensitized rats that the immediate response to endointestinal challenge with allergen (10^-6 M ovalbumin) is characterized by mucosal exudation of plasma with little or no concomitant change in the mucosal absorption capacity. The luminal entry of plasma macromolecules also leaves the light microscopic structure and the ultrastructure of the mucosa unaffected. It is possible that the plasticity of epithelial zonulae occludens allows a noninjurious and unidirectional paracellular flux of extravasated plasma into the gut lumen. We propose that inflammatory-stimulus-induced mucosal exudation of plasma belongs to the first-line defense mechanisms of the intact lining of the intestine.     

The effects of contignasterol (IZP-94,005) on allergen-induced plasma protein exudation in the tracheobronchial airways of sensitized guinea - pigs in vivo

OBJECTIVE: To examine contignasterol (marine-derived) on allergen-induced plasma exudation in the tracheobronchial airways. MATERIAL: English shorthair guinea-pigs actively sensitized to ovalbumin. TREATMENT: 21 to 36 days after sensitization, contignasterol, budesonide or nedocromil and then ovalbumin (12 pmol) were superfused onto the tracheal mucosa (i. t.) of anaesthetized animals. METHODS: Tracer (125I-human serum albumin) was measured in tracheobronchial lavage. RESULTS: Thirty min after administration of contignasterol (100 and 200, but not 0.2 or 2.0 microg/kg), budesonide or nedocromil (200 microg/kg), the ovalbumin response (plasma exudate, microl) was significantly inhibited. The response was also inhibited 5 min after 200 microg/kg nedocromil but not after contignasterol or budesonide. CONCLUSIONS: Contignasterol was topically active and showed anti-inflammatory effects in the tracheobronchial airways in that it inhibited allergen-induced plasma protein exudation.     

Contribution of Plasma-Derived Molecules to Mucosal Immune Defence, Disease and Repair in the Airways

This review discusses recent observations, in health and disease, on the release and distribution of plasma-derived molecules in the airway mucosa. Briefly, the new data on airway mucosal exudation mechanisms suggest that the protein systems of plasma contribute significantly to the mucosal biology, not only in injured airways but also in such mildly inflamed airways that lack oedema and exhibit no sign of epithelial derangement. Plasma as a source of pluripotent growth factor, adhesive, leucocyte-activating, etc., molecules may deserve a prominent position in schemes that claim to illustrate immunological and inflammatory mechanisms of the airway mucosa in vivo .     

Effects of neutrophil-derived oxidants on intestinal permeability,electrolyte transport,and epithelial cell viability

There are several pathophysiologic conditions in which intestinal inflammation is associated with enhanced mucosal permeability, fluid loss, and epithelial cell injury. The objective of this study was to determine the effects of polymorphonuclear leukocyte (PMN) -derived oxidants on ileal mucosal permeability in vivo as well as electrolyte transport and epithelial cell viability in vitro. Using blood-tolumen clearance of [⁵¹Cr]EDTA as a measure of mucosal permeability, we found that luminal perfusion with hydrogen peroxide (H₂O₂), hypochlorous acid (HOCl), or monochloramine (NH₂Cl) produced a dose-dependent increase in mucosal permeability. Perfusion with 0.1 mM, 0.5 mM, and 1.0 mM oxidant produced a 2±1, 5±2, and 11±5-fold increase in mucosal permeability for H₂O₂, a 2±1, 8±3, and 36±12-fold increase for HOC1, and a 3±1, 11±2, and 30±7-fold increase for NH₂Cl. Taurine monochloramine (TauNHCl) was ineffective in enhancing the blood-to-lumen clearance of [⁵¹Cr]EDTA. Furthermore, 0.01 mM and 0.1 mM NH₂Cl and H₂O₂ produced significant increases in short-circuit current across rat ileum in vitro, whereas HOC1 and TauNHCl were without effect. Tissue resistance and potential difference were not altered, suggesting that NH₂Cl, HOCl, and H₂O₂ were not cytotoxic under these conditions. Cultured intestinal epithelial cells exposed to NH₂Cl and HOCl were injured in a dose-dependent manner in vitro, whereas H₂O₂ and TauNHCl were nontoxic. Taken together, our data suggest that PMN-derived oxidants may mediate the enhanced mucosal permeability, electrolyte transport, and epithelial cell injury associated with acute inflammation of the bowel.Supported by grants from the National Institutes of Health (DK 39168 and DK 33594).     

Mucosal exudation in respiratory defence: neural or non-neural control?

In human and animal airways, mucosal exudation of unfiltered plasma occurs promptly in response to inflammatory provocations (allergen, occupational factors, mediators). Mucosal exudation is distinctly an increase in outward permeability of vascular-mucosal barriers and it leaves the epithelial lining intact. Through its volume, its proteins including immunoglobulins, its enzyme systems and its newly generated peptides, the plasma exudate constitutes a comprehensive first-line mucosal defence. In rodent, but not in human airways, tachykinin neuropeptides have a demonstrated capacity to produce mucosal exudation.     

Hydrogen peroxide induces DNA single strand breaks in respiratory epithelial cells

The respiratory epithelium is often exposed to oxidant gases, including ozone from photochemical smog and toxic oxygen metabolites released from neutrophils recruited in conditions of airway inflammation. We evaluated DNA single strand break formation by alkaline elution as a measure of oxidant-induced DNA damage to bronchial epithelial cells. Human AdenoSV-40-transformed bronchial epithelial cells (BEAS), subclone R1.4 or nonhuman primate bronchial epithelial cells were cultured in growth factor supplemented Ham's F12 medium on polycarbonate filters. DNA was labeled by incubation with [³H]thymidine. Cells were incubated for 1 h in HBSS or HBSS and increasing concentrations of hydrogen peroxide (H₂O₂). Cells incubated in H₂O₂ demonstrated dose-dependent increases in strand break formation, and BEAS cells were more sensitive to H₂O₂-induced injury than primary bronchial epithelial cells. The addition of catalase or preincubation of cells with the iron chelator desferoxamine prevented H₂O₂-induced strand breakage. DNA strand break formation may be an important mechanism of oxidant injury in respiratory epithelial cells.This work was supported by NIEHS grant ES-00628 and California Primate Research Center Base grant. Portions of this work were presented at the American Thoracic Society annual meeting, May 1992, Miami, Florida.     

Regulation of the epithelial Na+ channel and airway surface liquid volume by serine proteases

Mammalian airways are protected from infection by a thin film of airway surface liquid (ASL) which covers airway epithelial surfaces and acts as a lubricant to keep mucus from adhering to the epithelial surface. Precise regulation of ASL volume is essential for efficient mucus clearance and too great a reduction in ASL volume causes mucus dehydration and mucus stasis which contributes to chronic airway infection. The epithelial Na⁺ channel (ENaC) is the rate-limiting step that governs Na⁺ absorption in the airways. Recent in vitro and in vivo data have demonstrated that ENaC is a critical determinant of ASL volume and hence mucus clearance. ENaC must be cleaved by either intracellular furin-type proteases or extracellular serine proteases to be active and conduct Na⁺, and this process can be inhibited by protease inhibitors. ENaC can be regulated by multiple pathways, and once proteolytically cleaved ENaC may then be inhibited by intracellular second messengers such as cAMP and PIP₂. In the airways, however, regulation of ENaC by proteases seems to be the predominant mode of regulation since knockdown of either endogenous serine proteases such as prostasin, or inhibitors of ENaC proteolysis such as SPLUNC1, has large effects on ENaC activity in airway epithelia. In this review, we shall discuss how ENaC is proteolytically cleaved, how this process can regulate ASL volume, and how its failure to operate correctly may contribute to chronic airway disease.     

Dioscorin Pre-treatment Protects A549 Human Airway Epithelial Cells from Hydrogen Peroxide-Induced Oxidative Stress

Hydrogen peroxide (H₂O₂) is a highly reactive oxygen species involved in lung and bronchial epithelium injury. Increased H₂O₂ levels have been reported in expired breath condensates of patients with inflammatory airway diseases such as chronic obstructive pulmonary disease. Protecting airway epithelial cells from oxidative stress is an important task in the prevention and management of airway diseases. Previous studies demonstrate that yam (Dioscorea batatas Decne) has antioxidant and anti-trypsin activities. This study evaluated the validity of dioscorin in vitro. The results showed that dioscorin attenuated the alteration of H₂O₂ on G2/M cell cycle arrest. This might be associated with the activation of IκB and subsequent inactivation of NF-κB. Furthermore, dioscorin suppressed IL-8 secretion and reduced changes of adhesion molecule expressions in H₂O₂-injured A549 cells. These results help in understanding the potential of traditional Chinese herbal medicine as treatment for airway inflammatory diseases.     

Vascular changes in rabbit skin induced by proinflammatory phorbol and 12-deoxyphorbol esters

The effects of proinflammatory phorbol and 12-deoxyphorbol esters were determined on blood flow changes and plasma exudation in rabbit skin. Blood flow changes were measured by means of¹³³Xe washout over that in control-treated sites, while plasma exudation was measured by¹³¹I-labeled human serum albumin leakage from skin blood vessels. 12-Deoxyphorbol-13-phenylacetate, 12-deoxyphorbol-13-angelate, and their C-20 acetates induced vasoconstriction in rabbit skin in doses of 100 ng/site. Tetradecanoyl phorbol acetate induced vasoconstriction to a far lower degree, while the parent alcohol phorbol and 9,13,14-orthophenylacetyl-resiniferonol had no significant effects on rabbit microvasculature. The ability of tigliane esters to contract rabbit blood vessels was confirmed in vitro in that each of these esters induced a prolonged contraction of superfused rabbit aorta in doses of 1–5g. Plasma exudation in rabbit skin was not significantly increased by the phorbol and 12-deoxyphorbol esters, but in a second determination using 100 ng of PGE₁ together with 100 ng of ester, plasma exudations of up to 40l per site were recorded.     

Anti-asthma drugs and capsaicine-induced microvascular effects in lower airways

Substance P, capsaicine and bicervical vagal stimulation may increase microvascular permeability to macromolecules in lower airways. In previous studies techniques were employed that could have adversely affected the microvasculature. An atraumatic method of exposing the guinea-pig trachea to constant concentrations of drugs followed by quantitation of the blood-pool (in vivo ⁹⁹Tc^m-labelled erythrocytes) and extravasated macromolecules (Fitc.-dextran) has now been developed. Capsaicine produced marked extravasation of Fitc.-dextran while substance P in the concentration tested merely had vasodilator properties. Pretreatment with lidocaine, the -receptor agonist, terbutaline, or the adenosine non-blocking xanthine, enprofylline, inhibited the capsaicine induced inflammatory response.     

Use of micro-CT to determine tracheobronchial airway geometries in three strains of mice used in inhalation toxicology as disease models

Aerosol dosimetry estimates for mouse strains used as models for human disease are not available, primarily because of the lack of tracheobronchial airway morphometry data. By using micro-CT scans of in-situ prepared lung casts, tracheobronchial airway morphometry for four strains of mice were obtained: Balb/c, AJ, C57BL/6, and Apoe^−/−. The automated tracheobronchial airway morphometry algorithms for airway length and diameter were successfully verified against previously published manual and automated tracheobronchial airway morphometry data derived from two identical in-situ Balb/c mouse lung casts. There was also excellent agreement in tracheobronchial airway length and diameter between the automated and manual airway data for the AJ, C57BL/6, and Apoe^−/− mice. Differences in branch angle measurements were partially due to the differences in definition between the automated algorithms and manual morphometry techniques. Unlike the manual airway morphometry techniques, the automated algorithms were able to provide a value for inclination to gravity for each airway. Inclusion of an inclination to gravity angle for each airway along with airway length, diameter, and branch angle make the current automated tracheobronchial airway data suitable for use in dosimetry programs that can provide dosimetry estimates for inhaled material. The significant differences in upper tracheobronchial airways between Balb/c mice and between C57BL/6 and Apoe^−/− mice highlight the need for mouse strain-specific aerosol dosimetry estimates.