Importance of airway blood flow on particle clearance from the lung

Wagner, Elizabeth M., and W. Michael Foster. Importanceof airway blood flow on particle clearance from the lung.J. Appl. Physiol. 81(5):1878-1883, 1996.The role of the airway circulation insupporting mucociliary function has been essentially unstudied. Weevaluated the airway clearance of inert, insoluble particles inanesthetized ventilated sheep (n = 8),in which bronchial perfusion was controlled, to determine whetherairway mucosal blood flow is essential for maintaining surfacetransport of particles through airways. The bronchial branch of thebronchoesophageal artery was cannulated and perfused with autologousblood at control flow (0.6 ml ^· min^{1 ·} kg¹)or perfusion was stopped. With the sheep in a supine position and aftera steady-state ¹³³Xe ventilationscan for designation of lung zones of interest, an inert^99mTc-labeled sulfur colloidaerosol (2.1-µm diameter) was deposited in the lung. The clearancekinetics of the radiolabeled particles were determined from theactivity-time data obtained for right and left lung zones. At 60 minpostdeposition of aerosol, average airway particle retention forcontrol bronchial blood flow conditions was 57 ± 7 (SE)% for theright and 53 ± 8% for the left lung zones. Clearance of particleswas significantly impaired when bronchial blood flow was stopped, e.g.,right and left lung zones averaged 77 ± 6 and 76 ± 7% at 60 min, respectively (P < 0.05). Thesedata demonstrate a significant influence of the bronchial circulation on mucociliary transport of insoluble particles. Potential mechanisms that may account for these results include the importance of the bronchial circulation for nutrient flow, maintenance of airway walltemperature and humidity, and release of mediators and sequelae associated with tissue ischemia.

     

Budesonide affects allergic mucociliary dysfunction

Airwayinflammation characterized by neutrophils and free elastase contributesto allergic mucociliary dysfunction. Glucocorticosteroids are the mostimportant anti-inflammatory agents used in the treatment of asthma, buttheir effect on allergic mucociliary dysfunction is not known.Therefore, we assessed both the prophylactic and therapeutic effects ofthe glucocorticosteroid budesonide on antigen-induced mucociliarydysfunction in sheep. Tracheal mucus velocity (TMV), amarker of mucociliary clearance, was measured by using aroentgenographic technique. When budesonide was administered either 30 min before or 1 h after airway challenge with Ascarissuum, the antigen-induced fall in TMV at 6 h wasprevented. The effects on TMV at 8 and 24 h after challenge were alsodetermined when budesonide and, for comparative purposes,₁-protease inhibitor were given6 h after antigen challenge. Budesonide treatment improved TMV at 8 h,but TMV was not significantly different from antigen alone at 24 h.Treatment with ₁-proteaseinhibitor, however, caused only a significant reversal of theantigen-induced fall in TMV at 24 h after challenge; this indicates amore prolonged effect than budesonide. Our results suggest thatantiproteases may have a potential role as a therapeutic approach tomucociliary dysfunction in asthma and provide evidence for anothermeans by which glucocorticosteroids contribute to the control of thedisease.

     

Bronchial airway deposition and retention of particles in inhaled boluses: effect of anatomic dead space

The fractionaldeposition of particles in boluses delivered to shallow lung depths andtheir subsequent retention in the airways may depend on the relativevolume and size of an individual's airways. To evaluate the effect ofvariable anatomic dead space (ADS) on aerosol bolus delivery we hadhealthy subjects inhale radiolabeled, monodisperse aerosol(^99mTc-iron oxide, 3.5 µm meanmondispersed aerosol diameter) boluses (40 ml) to a volumetric frontdepth of 70 ml into the lung at a lung volume of 70% total lungcapacity end inhalation. By using filter techniques, aerosolphotometry, and gamma camera analysis, we estimated the fraction of theinhaled boluses deposited in intrathoracic airways (IDF). ADS bysingle-breath N₂ washout was alsomeasured from 70% total lung capacity. Results showed that among allsubjects IDF was variable (range = 0.04-0.43, coefficient ofvariation = 0.54) and increased with decreasing ADS(r = 0.76, P = 0.001, n = 16). We found significantlygreater deposition in the left (L) vs. right (R) lungs; mean L/R (ratioof deposition in L lung to R lung, normalized to ratio of L-to-R lungvolume) was 1.58 ± 0.42 (SD; P < 0.001 for comparison with 1.0). Retention of deposited particles at 2 hwas independent of ADS or IDF. There was significant retention ofparticles at 24 h postdeposition (0.27 ± 0.05) andslow clearance of these particles continued through 48 hpostdeposition. Finally, analysis of central-to-peripheral ratios ofinitial deposition and 24-h-retention gamma-camera images suggestsignificant retention of insoluble particles in large bronchial airwaysat 24 h postdeposition (i.e., 24 h central-to-peripheral ratio = 1.40 ± 0.44 and 1.82 ± 0.54 in the R and L lung, respectively; P < 0.02 for comparison with 1.0).These data may prove useful for 1)designing aerosol delivery techniques to target bronchial airways and2) understanding airway retention ofinhaled particles.

     

Regional deposition and retention of particles in shallow, inhaled boluses: effect of lung volume

The regionaldeposition of particles in boluses delivered to shallow lung depths andtheir subsequent retention in the airways may depend on the lung volumeat which the boluses are delivered. To evaluate the effectof end-inspiratory lung volume on aerosol bolus delivery, we hadhealthy subjects inhale radiolabeled, monodisperse aerosol(^99mTc-iron oxide, 3.5-µm massmedian aerodynamic diameter) boluses (40 ml) to a volumetric frontdepth of 70 ml into the lung at lung volumes of 50, 70, and 85% oftotal lung capacity (TLC) end inhalation. By gamma camera analysis, wefound significantly greater deposition in the left (L) vs. right (R)lungs at the 70 and 85% TLC end inhalation; ratio of deposition in Lto R lung, normalized to L-to-R ratio of lung volume (mean L/R), was1.60 ± 0.45 (SD) and 1.96 ± 0.72, respectively(P < 0.001 for comparison to 1.0) for posterior images. However, at 50% TLC, L/R was 1.23 ± 0.37, not significantly different from 1.0. These data suggest that the L andR lungs may be expanding nonuniformly at higher lung volumes. On theother hand, subsequent retention of deposited particles at 2 and 24 hpostdeposition was independent of L/R at the various lung volumes. Thusasymmetric bolus ventilation for these very shallow boluses does notlead to significant increases in peripheral alveolar deposition. Thesedata may prove useful for 1)designing aerosol delivery techniques to target bronchial airways and2) understanding airway retention ofinhaled particles.

     

Supercritical fluid-aerosolized vitamin E pretreatment decreases leak in isolated oxidant-perfused rat lungs

Hybertson, Brooks M., Roger P. Kitlowski, Eric K. Jepson,and John E. Repine. Supercritical fluid-aerosolized vitamin Epretreatment decreases leak in isolated oxidant-perfused rat lungs.J. Appl. Physiol. 84(1): 263-268, 1998.We hypothesized that direct pulmonary administration ofsupercritical fluid-aerosolized (SFA) vitamin E would decrease acuteoxidative lung injury. We previously reported that rapid expansion ofsupercritical CO₂ formedrespirable particles of vitamin E and that administering SFA vitamin Eto rats increased lung vitamin E levels and decreased neutrophil-mediated lung leak. In the present investigation, we foundthat pretreatment with SFA vitamin E protected isolated rat lungsagainst the oxidant-induced lung leak caused by perfusion with xanthineoxidase (XO) and purine, an enzyme system that generates superoxideanion () and hydrogenperoxide. SFA vitamin E droplets were 0.7-3 µm in diameter, andinhalation of the airborne droplets for 30 min deposited ~55 µg ofvitamin E in rat lungs. Isolated rat lungs perfused with XO (0.02 U/ml) and purine (10 mM) gained more weight (1.75 ± 0.12 g,n = 8), retained more Ficoll(11.5 ± 1.2 mg/left lung,n = 7), and accumulated more Ficoll intheir lung lavages (700 ± 146 µg/ml,n = 8) than control lungs [0.25 ± 0.06 g (n = 10), 6.2 ± 1.2 mg/left lung (n = 9), and 141 ± 31 µg/ml (n = 8), respectively,P < 0.05]. In contrast,isolated lungs from rats that were pretreated with SFA vitamin E haddecreased (P < 0.05) weight gains(0.32 ± 0.06 g, n = 7), Ficollretentions (3.3 ± 1.1 mg/left lung,n = 7), and lung lavage Ficollconcentrations (91 ± 26 µg/ml,n = 6) after perfusion with XO andpurine compared with isolated lungs from control rats perfused with XOand purine. This protective effect was not observed in rat lungs givensham treatments (CO₂ alone orvitamin E acetate aerosolized with supercriticalCO₂). Our results suggest thatdirect pulmonary supplementation of vitamin E decreases susceptibilityto vascular leakage caused by XO-derived oxidants.

     

Effect of microgravity and hypergravity on deposition of 0.5-to 3-m-diameter aerosol in the human lung

Darquenne, Chantal, Manuel Paiva, John B. West, and G. KimPrisk. Effect of microgravity and hypergravity on deposition of0.5- to 3-µm-diameter aerosol in the human lung. J. Appl. Physiol. 83(6): 2029-2036, 1997.Wemeasured intrapulmonary deposition of 0.5-, 1-, 2-, and 3-µm-diameterparticles in four subjects on the ground (1 G) and during parabolicflights both in microgravity (µG) and at ~1.6 G. Subjects breathed aerosols at a constant flow rate (0.4 l/s) and tidalvolume (0.75 liter). At 1 G and ~1.6 G, deposition increased withincreasing particle size. In µG, differences in deposition as afunction of particle size were almost abolished. Deposition was anearly linear function of the G level for 2- and 3-µm-diameterparticles, whereas for 0.5- and 1.0-µm-diameter particles, depositionincreased less between µG and 1 G than between 1 G and ~1.6 G. Comparison with numerical predictions showed good agreement for 1-, 2-, and 3-µm-diameter particles at 1 and ~1.6 G, whereas the modelconsistently underestimated deposition in µG. The higher depositionobserved in µG compared with model predictions might be explained bya larger deposition by diffusion because of a higher alveolarconcentration of aerosol in µG and to the nonreversibility of theflow, causing additional mixing of the aerosols.

     

Regional deposition of inhaled particles in human lungs: comparison between men and women

We measured detailed regional depositionpatterns of inhaled particles in healthy adult male(n = 11; 25 ± 4 yr of age) and female (n = 11; 25 ± 3 yr of age)subjects by means of a serial bolus aerosol delivery technique formonodisperse fine [particle diameter(D_p) = 1 µm] and coarse aerosols(D_p = 3 and 5 µm). The bolus aerosol (40 ml half-width) was delivered to a specificvolumetric depth (Vp) of the lung ranging from 100 to 500 ml with a50-ml increment, and local deposition fraction (LDF) was assessed for each of the 10 local volumetric regions. In all subjects, the deposition distribution pattern was very uneven with respect to Vp,showing characteristic unimodal curves with respect to particle sizeand flow rate. However, the unevenness was more pronounced in women.LDF tended to be greater in all regions of the lung in women than inmen for D_p = 1 µm. For D_p = 3 and 5 µm, LDF showed a marked enhancement in the shallow region of Vp  200 ml in women compared with men(P < 0.05). LDF in women wascomparable to or smaller than those of men in deep lung regions of Vp > 200 ml. Total lung deposition was comparable between men and womenfor fine particles but was consistently greater in women than men forcoarse particles regardless of flow rates used: the difference rangedfrom 9 to 31% and was greater with higher flow rates(P < 0.05). The results indicatethat 1) particledeposition characteristics differ between healthy men and women undercontrolled breathing conditions and2) deposition in women is greaterthan that in men.

     

Elastic moduli of excised constricted rat lungs

When airways constrict, the surrounding parenchyma undergoesstretch and distortion. Because of the mechanical interdependence between airways and parenchyma, the material properties of the parenchyma are important factors that modulate the degree ofbronchoconstriction. The purpose of this study was to investigate theeffect of changes in transpulmonary pressure (Ptp) and inducedconstriction on parenchymal bulk (k)and shear (µ) moduli. In excised rat lungs, pressure was measured atthe airway opening, and pressure-volume curves were obtained byimposing step decreases in volume with a calibrated syringe from totallung inflation. Calculation was made ofk during small-volume oscillations (1 Hz). Absolute lung volume at 0 cmH₂O Ptp was obtained bysaline displacement. To calculate µ, a lung-indentation test wasperformed. The lung surface was deformed with a cylindrical punch(diameter = 0.45 cm) in 0.25-mm increments, and the force required toeffect this displacement was measured by a weight balance. Measurementsof k and µ were obtained at 4 and 10 cmH₂O Ptp, and again at 4 cmH₂O Ptp, after delivery ofmethacholine aerosol (100 mg/ml) into the trachea. Values ofk and µ in rat lungs were similar tothose reported in other species. In addition, k and µ were dependent on Ptp. Afterinduced constriction, k and µ increased significantly. That k and µ can increase after induced constriction has important implicationsvis a vis the factors modulating airway narrowing.

     

Maintenance of myonuclear domain size in rat soleus after overload and growth hormone/IGF-I treatment

The purpose ofthis study was to determine the effects of functional overload (FO)combined with growth hormone/insulin-like growth factor I (GH/IGF-I)administration on myonuclear number and domain size in rat soleusmuscle fibers. Adult female rats underwent bilateral ablation of theplantaris and gastrocnemius muscles and, after 7 days of recovery, wereinjected three times daily for 14 days with GH/IGF-I (1 mg/kg each; FO + GH/IGF-I group) or saline vehicle (FO group). Intact rats receivingsaline vehicle served as controls (Con group). Muscle wet weight was32% greater in the FO than in the Con group: 162 ± 8 vs. 123 ± 16 mg. Muscle weight in the FO + GH/IGF-I group (196 ± 14 mg) was59 and 21% larger than in the Con and FO groups, respectively. Meansoleus fiber cross-sectional area of the FO + GH/IGF-I group (2,826 ± 445 µm²) was increasedcompared with the Con (2,044 ± 108 µm²) and FO (2,267 ± 301 µm²) groups. The difference infiber size between the FO and Con groups was not significant. Meanmyonuclear number increased in FO (187 ± 15 myonuclei/mm) and FO + GH/IGF-I (217 ± 23 myonuclei/mm) rats compared with Con (155 ± 12 myonuclei/mm) rats, although the difference between FO and FO + GH/IGF-I animals was not significant. The mean cytoplasmic volume permyonucleus (myonuclear domain) was similar across groups. These resultsdemonstrate that the larger mean muscle weight and fibercross-sectional area occurred when FO was combined with GH/IGF-Iadministration and that myonuclear number increased concomitantly withfiber volume. Thus there appears to be some mechanism(s) that maintainsthe myonuclear domain when a fiber hypertrophies.

     

Effect of ozone on the postnatal development of lamb mucociliary apparatus

We determined whether exposure to O3 early in the postnatal period impairs the normal development of the mucociliary apparatus in lambs and whether such changes lead to prolonged abnormalities in mucociliary function. Lambs were exposed to air (controls) or to 1 ppm O3 for 4 h/day for 5 days during the 1st wk of life. Tracheal mucus velocity (TMV), a marker of lung mucociliary clearance, was measured in vivo at birth (0 wk) and up to 24 wk later, and tracheal secretory function was measured (in vitro) and the morphology of the tracheal mucosa was determined at 0 and 2 wk in both groups. In the control group, TMV increased 94% from 0 to 2 wk (P less than 0.05), continued to increase until reaching a plateau at 8 wk, and then remained constant from 8 to 24 wk. In contrast, O3-exposed lambs showed a 24% decrease in TMV from 0 to 2 wk (P less than 0.05 vs. control), and throughout the remaining time TMV remained below (P less than 0.05) that observed in control lambs. O3 exposure partially prevented the age-dependent decrease in basal secretion of tracheal macromolecules normally observed between 0 and 2 wk. These changes in secretory function were associated with a significant increase in tissue conductance (37%, P less than 0.05 vs. 0 wk), predominantly the result of active chloride secretion. The functional changes induced by O3 were associated with a retardation of the normal morphological development of the tracheal epithelium.(ABSTRACT TRUNCATED AT 250 WORDS)     

Genistein activates CFTR-mediated Cl(-) secretion in the murine trachea and colon

The action of the isoflavonegenistein on the cystic fibrosis transmembrane conductance regulator(CFTR) has been studied in many cell systems but not in intact murinetissues. We have investigated the action of genistein on murine tissuesfrom normal and cystic fibrosis (CF) mice. Genistein increased theshort-circuit current (I_sc) in tracheal(16.4 ± 2.8 µA/cm²) and colonic (40.0 ± 4.4 µA/cm²) epithelia of wild-type mice. This increase wasinhibited by furosemide, diphenylamine-2-carboxylate, andglibenclamide, but not by DIDS. In contrast, genistein produced nosignificant change in the I_sc of the trachealepithelium (0.9 ± 1.1 µA/cm²) and decreased theI_sc of colons from CF null (13.1 ± 2.3 µA/cm²) and F508 mice (10.3 ± 1.3 µA/cm²). Delivery of a human CFTRcDNA-liposome complex to the airways of CF null mice restored thegenistein response in the tracheas to wild-type levels. Tracheas fromF508 mice were also studied: 46% of trachea showed no response togenistein, whereas 54% gave an increase in I_scsimilar to that in wild type. We conclude that genistein activatesCFTR-mediated Cl secretion in the murine trachea anddistal colon.

     

Role of neutrophils in lung vascular injury and edema after premature birth in lambs

Carlton, David P., Kurt H. Albertine, Soo Chul Cho, MennoLont, and Richard D. Bland. Role of neutrophils in lung vascular injury and edema after premature birth in lambs. J. Appl. Physiol. 83(4): 1307-1317, 1997.Toinvestigate the role of neutrophils in the pathogenesis of respiratorydistress after premature birth, we assessed the relationship betweencirculating neutrophil concentration and neutrophil accumulation in thelung, lung lymph and pleural liquid flow, and extravascular lungwater in 10 chronically catheterized preterm lambs (127 ± 1 days gestation) that were mechanically ventilated for 8 h afterbirth. Circulating neutrophil concentration transiently decreasedwithin 2 h after birth and then returned to prenatal values by 6-8h. The decrease in circulating neutrophil concentration was relateddirectly to the accumulation of neutrophils in the air spaces, drainageof liquid and protein from the lung 6-8 h after delivery, andpostmortem extravascular lung water. In additional studies, weintravenously administered mechlorethamine to 5 fetal lambs to reducecirculating neutrophils before delivery (neutrophil concentrationbefore birth: 9 ± 11 cells/µl). Compared with control lambs,neutrophil-depleted lambs had significantly less drainage of liquid(7.8 ± 5.9 vs. 2.6 ± 1.9 ml/h, respectively) and protein (116 ± 74 vs. 42 ± 27 mg/h, respectively) from the lung 6-8 hafter birth and significantly less extravascular lung water atpostmortem (6.5 ± 0.8 vs. 4.8 0.6 g/g dry lung,respectively). Thus neutrophils contribute to thepathogenesis of respiratory distress after premature birth byincreasing lung vascular protein permeability and promoting lung edema.

     

Embryonic Chicken Trachea as a New In Vitro Model for the Investigation of Mucociliary Particle Clearance in the Airways

Mucociliary clearance (MC) is an important defense mechanism of the respiratory system to eliminate inhaled and possibly noxious particles from the lung. Although the principal mechanics of MC seem to be relatively clear there are still open questions regarding the long-term clearance of particles. Therefore, we have developed a new set-up based on embryonic chicken trachea (ECT) to investigate mucociliary particle clearance in more detail. ECT was placed in an incubation chamber after carbon particles were applied and tracked using optical microscopy. The aim of the study was to validate this model by investigating the impact of temperature, humidity and drugs on particle transport rates. Particles were transported reproducibly along the trachea and clearance velocity (2.39 ± 0.25) mm/min was found to be in accordance to data reported in literature. Variation in temperature resulted in significantly reduced MC: (0.40 ± 0.12) mm/min (20 °C); (0.42 ± 0.10) mm/min (45 °C). Decreasing humidity (99–60%) had no significant effect on MC, whereas reduction to 20% humidity showed a significant influence on particle clearance. The use of different cilio- and muco-active drugs (Propranolol, Terbutalin, N-acetylcysteine) resulted in altered MC according to the pharmacological effect of the substances: a concentration dependent decrease of MC was found for Propranolol. From our results we conclude that this model can be employed to investigate MC of particles in more detail. Hence, the model may help to understand and identify decisive physico-chemical parameters for MC and to answer open questions regarding the long-term clearance phenomenon. Electronic supplementary material  The online version of this article (doi:) contains supplementary material, which is available to authorized users.     

Na+-K+-ATPase in frog esophagus mucociliary cell membranes: inhibition by protein kinase C activation

We examined protein kinase C (PKC)-dependentregulation ofNa⁺-K⁺-ATPasein frog mucociliary cells. Activation of PKC by12-O-tetradecanoylphorbol-13-acetate (TPA) or 1,2-dioctanoyl-sn-glycerol(diC8) either in intact cells or isolated membranes resulted in aspecific inhibition ofNa⁺-K⁺-ATPaseactivity by ~25-45%. The inhibitory effects in membranes exhibited time dependence and dose dependence [half-maximalinhibition concentration (IC₅₀) = 0.5 ± 0.1 nM and 2.4 ± 0.2 µM, respectively, for TPA anddiC8] and were not influenced byCa²⁺. Analysis of the ouabaininhibition pattern revealed the presence of twoNa⁺-K⁺-ATPaseisoforms with IC₅₀ values forcardiac glycoside of 2.6 ± 0.8 nM and 409 ± 65 nM,respectively. Most importantly, the isoform possessing a higheraffinity for ouabain was almost completely inhibited by TPA, whereasits counterpart was hardly sensitive to the PKC activator. The resultssuggest that, in frog mucociliary cells, PKC regulatesNa⁺-K⁺-ATPaseand that this action is related to the specificNa⁺-K⁺-ATPaseisoform.

     

Aerosolized manganese SOD decreases hyperoxic pulmonary injury in primates. I.Physiology and biochemistry

Simonson, Steven G., Karen E. Welty-Wolf, Yuh-Chin T. Huang,David E. Taylor, Stephen P. Kantrow, Martha S. Carraway, James D. Crapo, and Claude A. Piantadosi. Aerosolizedmanganese SOD decreases hyperoxic pulmonary injury in primates. I. Physiology and biochemistry. J. Appl.Physiol. 83(2): 550-558, 1997.Prolonged hyperoxia causes lung injury andrespiratory failure secondary to oxidative tissue damage mediated, inpart, by the superoxide anion. We hypothesized that aerosol treatmentwith recombinant human manganese superoxide dismutase (rhMnSOD) wouldattenuate hyperoxic lung damage in primates. Adult baboons wereanesthetized and ventilated with 100% oxygen for 96 h or until death.Six animals were treated with aerosolized rhMnSOD (3 mg · kg¹ · day¹in divided doses), and six control animals did not receive enzyme therapy. Physiological variables were recorded every 12 h, and ventilation-perfusion ratio relationships were evaluated by using themultiple inert-gas elimination technique. After the experiments, surfactant composition and lung edema were measured. We found thatrhMnSOD significantly decreased pulmonary shunt fraction (P < 0.01) and preserved arterialoxygenation (P < 0.01) during hyperoxia. The rhMnSOD increased lung phospholipids,phosphatidylcholine and disaturated phosphatidylcholine, and decreasedlung edema in this model. Testing of higher and lower doses of MnSOD (1 and 10 mg · kg¹ · day¹)in two other groups of baboons produced variable physiological protection, suggesting a "window" of effective dosage. Weconclude that aerosolized MnSOD (3 mg · kg¹ · day¹)affords significant preservation of pulmonary gas exchange during hyperoxic lung injury.

     

Effect of Diazinon PLUS on rapidly adapting receptors in the rabbit

Campbell, Hillary, Krishnan Ravi, Emigdio Bravo, and C. Tissa Kappagoda. Effect of Diazinon PLUS on rapidly adapting receptors in the rabbit. J. Appl.Physiol. 81(6): 2604-2610, 1996.The effects ofDiazinon PLUS aerosol on the activities of rapidly adapting receptors(RARs) and slowly adapting receptors (SAR) of the airways wereinvestigated in anesthetized rabbits. The effects on boththe baseline activity and the responses to stimulation by increasingmean left atrial pressure were examined. Action potentialswere recorded from the left cervical vagus nerve. Aerosols (particlesize 3 µm) were generated by a Mini-HEART nebulizer. We observed thatan aerosol of Diazinon PLUS (1:10 vol/vol dilution in normal saline)decreased the baseline RAR activity (n = 10) significantly (P < 0.05) from209 ± 77 to 120 ± 40 impulses/min. In the post-Diazinon PLUScontrol period, the RAR activity recovered partially to 185 ± 75 impulses/min and decreased significantly to 131 ± 52 impulses/min(P < 0.05) after a second exposureof Diazinon PLUS (undiluted) aerosol. Aerosols of normal saline in thecontrol state did not produce a significant change in the RAR activity.A group of SAR (n = 8) were examinedunder similar conditions, and it was found that only the exposure toDiazinon PLUS (undiluted) aerosol decreased the activity significantly (P < 0.05) from 1,536 ± 206 to1,367 ± 182 impulses/min. The effect of Diazinon PLUS on theresponse to increasing mean left atrial pressure was examined in sevenRARs. In the control state, RAR activity increased significantly(P < 0.05) during elevation of meanleft atrial pressure. This response was abolished after exposure toDiazinon PLUS. These findings suggest that diazinon may interfere withairway defense mechanisms by reducing the activity of RARs.

     

Toxic copper level increases erythrocyte glycolytic rate,glutathione production and alters electrolyte balance in male Wistar rats

BackgroundCopper is a micronutrient vital to several cellular energy metabolic processes and drives erythropoiesis. However, it disrupts cellular biological activities and causes oxidative damage when in excess of cellular needs. This study investigated the effects of copper toxicity on erythrocyte energy metabolism in male Wistar rats.MethodsTen Wistar rats (150–170 g) were randomly divided into 2 groups: control (given 0.1 ml distilled water) and copper toxic (given 100 mg/kg copper sulphate). Rats were orally treated for 30 days. Blood, collected retro-orbitally after sodium thiopentone anaesthesia (50 mg/kg i.p.) into fluoride oxalate and EDTA bottles, was subjected to blood lactate assay and extraction of red blood cell respectively. Red blood cell nitric oxide (RBC NO), glutathione (RBC GSH), adenosine triphosphate (RBC ATP) levels, RBC hexokinase, glucose-6-phosphate (RBC G6P), glucose-6-phosphate dehydrogenase (RBC G6PDH), and lactate dehydrogenase (RBC LDH) activity was estimated spectrophotometrically. Values (Mean±SEM, n = 5) were compared by Student’s unpaired T-test at p < 0.05.Results and conclusionCopper toxicity significantly increased RBC hexokinase (23.41 ± 2.80 µM), G6P (0.48 ± 0.03 µM), G6PDH (71.03 ± 4.76nmol/min/ml) activities, ATP (624.70 ± 57.36 µmol/gHb) and GSH (3.08 ± 0.37 µM) level compared to control (15.28 ± 1.37 µM, 0.35 ± 0.02 µM, 330.30 ± 49.58 µmol/gHb, 54.41 ± 3.01nmol/min/ml and 2.05 ± 0.14 µM respectively, p < 0.05). Also, RBC LDH activity (145.00 ± 19.88mU/ml), NO (3.45 ± 0.25 µM) and blood lactate (31.64 ± 0.91 mg/dl) level were lowered significantly compared to control (467.90 ± 94.23mU/ml, 4.48 ± 0.18 µM and 36.12 ± 1.06 mg/dl respectively). This study shows that copper toxicity increases erythrocyte glycolytic rate and glutathione production. This increase could be connected to a compensatory mechanism for cellular hypoxia and increased free radical generation.     

Interaction between airway edema and lung inflation on responsiveness of individual airways in vivo

Brown, Robert H., Wayne Mitzner, and Elizabeth M. Wagner.Interaction between airway edema and lung inflation onresponsiveness of individual airways in vivo. J. Appl.Physiol. 83(2): 366-370, 1997.Inflammatorychanges and airway wall thickening are suggested to cause increasedairway responsiveness in patients with asthma. In fivesheep, the dose-response relationships of individual airways weremeasured at different lung volumes to methacholine (MCh) before andafter wall thickening caused by the inflammatory mediator bradykininvia the bronchial artery. At 4 cmH₂O transpulmonary pressure(Ptp), 5 µg/ml MCh constricted the airways to a maximum of 18 ± 3%. At 30 cmH₂O Ptp, MCh resultedin less constriction (to 31 ± 5%). Bradykinin increased airwaywall area at 4 and 30 cmH₂O Ptp(159 ± 6 and 152 ± 4%, respectively;P < 0.0001). At 4 cmH₂O Ptp, bradykinin decreasedairway luminal area (13 ± 2%; P < 0.01), and the dose-response curve was significantly lower (P = 0.02). At 30 cmH₂O, postbradykinin, the maximalairway narrowing was not significantly different (26 ± 5%;P = 0.76). Bradykinin produced substantial airway wall thickening and slight potentiation ofthe MCh-induced airway constriction at low lung volume. At high lung volume, bradykinin increased wall thickness but had no effecton the MCh-induced airway constriction. We conclude that inflammatoryfluid leakage in the airways cannot be a primary cause of airwayhyperresponsiveness.

     

Mechanical advantage of the canine diaphragm

The mechanical advantage (µ) of a respiratorymuscle is defined as the respiratory pressure generated per unit musclemass and per unit active stress. The value of µ can be obtained by measuring the change in the length of the muscle during inflation ofthe passive lung and chest wall. We report values of µ for themuscles of the canine diaphragm that were obtained by measuring thelengths of the muscles during a passive quasistatic vital capacitymaneuver. Radiopaque markers were attached along six muscle bundles ofthe costal and two muscle bundles of the crural left hemidiaphragms offour bred-for-research beagle dogs. The three-dimensional locations ofthe markers were obtained from biplane video-fluoroscopic images takenat four volumes during a passive relaxation maneuver from total lungcapacity to functional residual capacity in the prone and supinepostures. Muscle lengths were determined as a function of lung volume,and from these data, values of µ were obtained. Values of µ arefairly uniform around the ventral midcostal and crural diaphragm butsignificantly lower at the dorsal end of the costal diaphragm. Theaverage values of µ are 0.35 ± 0.18 and 0.27 ± 0.16 cmH₂O · g¹ · kg¹ · cm²in the prone and supine dog, respectively. These values are 1.5-2 times larger than the largest values of µ of the intercostal muscles in the supine dog. From these data we estimate that during spontaneous breathing the diaphragm contributes ~40% of inspiratory pressure inthe prone posture and ~30% in the supine posture. Passiveshortening, and hence µ, in the upper one-third of inspiratorycapacity is less than one-half of that at lower lung volume. The lower µ is attributed primarily to a lower abdominal compliance at highlung volume.

     

Effect of aerosolized acetylcholine on bronchial blood flow

We studiedthe effects of aerosolized as well as intravenous infusion ofacetylcholine on bronchial blood flow in six anesthetized sheep.Intravenous infusion of acetylcholine, at a dose of 2 µg/kg, increased bronchial blood flow from 45 ± 15 (SE) to 74 ± 30 ml/min, and vascular conductance increased by 76 ± 22%. In contrast, aerosolized acetylcholine at doses of 2 and 20 µg/kg decreased bronchial vascular conductance by ~10%. At anaerosolized dose of 200 µg/kg, the bronchial vascular conductanceincreased by ~15%, and there was no further increase in conductancewhen the aerosolized dose was increased to 2,000 µg/kg. Pretreatmentof animals with a nitric oxide synthase inhibitor,N-nitro-L-argininemethyl ester hydrochloride, partially blocked the vasodilatory effectsof intravenous acetylcholine and completely blocked the vasodilatoryeffects of high-dose aerosolized acetylcholine. These data suggest thataerosolized acetylcholine does not readily penetrate the vascular wallof bronchial circulatory system and, therefore, has minimalvasodilatory effects on the bronchial vasculature.