Synthetic
`hyperoxic
`
`surfactant
`lung
`injury
`
`scavenges oxidants
`
`and protects against
`
`A. PIANTADOSI
`AND CLAUDE
`L. YOUNG,
`STEPHEN
`J. FRACICA,
`J. GHIO, PHILIP
`ANDREW
`Medical Center and Division
`of Allergy, Critical Care, and Respiratory
`Veterans Administration
`Durham
`Medicine, Department of Medicine, Duke University Medical Center, Durham, North Carolina 27710
`
`L. Young,
`Stephen
`J. Fracica,
`J., Philip
`Ghio, Andrew
`scavenges
`surfactant
`Synthetic
`and Claude
`A. Piantadosi.
`J. Appl.
`lung
`injury.
`hyperoxic
`oxidants
`and protects
`against
`and mortality
`after
`Physiol.
`77(3): 1217-1223,
`1994.-Injury
`by surfactants
`that
`exposure
`to 100% oxygen can be diminished
`those
`responsible
`for
`may operate by mechanisms
`other
`than
`surface
`tension effects. We tested
`the hypotheses
`that 1) syn-
`thetic surfactant
`and
`its components
`function
`as antioxidants
`in vitro and 2) decrements
`in hyperoxic
`injury after
`treatment
`with a surfactant
`and
`its components
`are associated with de-
`creases
`in oxidativ
`te stress
`to the lung. A synthetic
`surfactant
`(Exosurf)
`and
`its non-surface-active
`components
`tyloxapol
`and cetyl alcohol were
`incubated
`in an
`iron-containing
`hy-
`droxyl
`radical-generating
`system
`to determine
`their abilities
`to
`prevent oxidation
`of deoxyribose. Doses of tyloxapol,
`cetyl alco-
`hol, and artificial
`surfactant
`diminished
`the absorbance
`of thio-
`barbituric
`acid-reactive
`products
`of deoxyribose.
`Similarly,
`ty-
`loxapol,
`cetyl alcohol,
`and the surfactant
`decreased
`hydroxyl-
`ated products
`of salicylate
`in
`the same system. Rats were
`instilled
`intratracheally
`with
`saline,
`tyloxapol,
`tyloxapol
`plus
`cetyl alcohol, or artificial
`surfactant
`and
`immediately
`exposed
`to air or 100% oxygen. After 61 h of oxygen exposure,
`pleural
`fluid volume and wet-to-dry
`lung weight
`ratios were decreased
`in animals
`treated
`with
`surfactant
`and/or
`its components.
`There were also decrements
`in
`thiobarbituric
`acid-reactive
`products of lung
`tissue.
`In separate experiments,
`mean survival
`of saline-treated
`rats exposed
`to 100% oxygen was 67.3 k 8.1 h
`and >96 h for rats given
`the surfactant
`or its components. We
`conclude
`that
`tyloxapol,
`cetyl alcohol,
`and Exosurf
`can
`func-
`tion as antioxidants
`in vitro and
`their
`in vivo
`instillation
`is
`associated with
`reduction
`in measures of hyperoxic
`injury, oxi-
`dized
`tissue products,
`and mortality.
`
`oxygen
`
`toxicity;
`
`free radicals;
`
`antioxidants
`
`is a combination of lipids,
`SURFACTANT
`PULMONARY
`proteins, and carbohydrates that provides alveolar stabil-
`ity at low lung volumes. The principal component (80%)
`of natural surfactant
`is phospholipid, most (5560%) of
`which is dipalmitoylphosphatidylcholine
`(DPPC), which
`is essential for surfactant activity
`(5). Surfactant
`lowers
`surface tension at the air-liquid
`interface, thus minimiz-
`ing or reducing alveolar collapse at end exhalation. Sur-
`factant deficiency or dysfunction
`leads to increased respi-
`ratory work, atelectasis, hypoxemia, and pulmonary
`edema . Lack of lung surfactant
`in newborns causes the
`
`infant respiratory distress synd rome (IRDS) , which re-
`sults in the deaths o f many untreated patients (1). Natu-
`ral surfactant and a commercial synthetic surfactant
`(Exosurf, Burroughs- Welcome) significantly decrease
`the mortality of IRDS (22, 24). Exosurf
`is a wholly syn-
`thetic surfactant containing DPPC, cetyl alcohol to solu-
`bilize the phospholipid, and the nonionic detergent ty-
`loxapol to disperse it.
`Supplemental oxygen is the therapy of choice to re-
`$3.00 Copyright 0 1994
`0161-7567/94
`
`verse arterial hypoxemia resulting from inadequate pul-
`monary exchange of oxygen. Prolonged exposures to
`high partial pressures of oxygen, however, induce a dif-
`fuse lung injury
`that includes abnormalities
`in the com-
`position, quantity, and function of surfactant
`(13, 18).
`Similar to IRDS, treatment of hyperoxic lung injury with
`exogenous natural surfactant or Exosurf can improve
`lung mechanics and gas exchange (l&17,23).
`The major
`action of surfactants has been assumed to be replace-
`ment of depleted or dysfunctional phospholipids,
`thus
`restoring surface tension toward normal (16). After ex-
`posures to hyperoxia, however, exogenous surfactant
`ameliorates defectiv pe epithe lial permeability
`(8, 23) and
`decreases mortality without
`improving
`lung compliance
`(17). These observations suggest a mechanism of action
`in addition to any effects of the drug on surface tension.
`Oxygen toxicity
`is mediated by an incomplete reduction
`of bimolecular oxygen, which generates reactive species
`including O,, H,O,, and . OH (11, 21). These partially
`reduced species of oxygen react with and damage biomo-
`lecules including enzymes, membrane l.ipids, and nucleic
`acids. In addition
`to improving mechanical and gas ex-
`change functions by lowering surface tension, therapy
`with surfactants after 100% oxygen may diminish oxida-
`tion of critical constituents of the lung.
`In this study, we tested three hypotheses: 1) synthetic
`surfactant and its components function as antioxidants
`in vitro; 2) decrements in hyperoxic
`injury after treat-
`ment with surfactant and its components are associated
`with evidence of decreased oxidative stress to the lung;
`and 3) injury and mortality after exposure to 100% oxy-
`gen can be diminished by components of a synthetic sur-
`factant other than those responsible for effects on sur-
`face tension.
`
`METHODS
`
`by
`Exosurf was donated
`surfactant
`The artificial
`Mczteriak.
`Burroughs-Wellcome
`(Research
`Triangle
`Park, NC). Tyloxa-
`pol, cetyl alcohol,
`and all other
`reagents were purchased
`from
`Sigma Chemical
`(St. Louis, MO) unless otherwise
`specified.
`In vitro assays for oxidant
`scavenging. The
`in vitro system
`employed
`to generate
`reactive oxygen
`species was a reaction
`mixture
`containing
`10.0 PM FeCl,, 1.0 mM ascorbate,
`and 1.0
`mM H,Oz
`in Hanks’ balanced
`salt solution
`(GIBCO, Grand
`Is-
`land, NY). The molecular
`target used in the first assay was the
`pentose
`sugar deoxyribose
`(1.0 mM), which
`reacts with oxi-
`dants
`to yield a mixture
`of products. On heating with
`thiobarbi-
`turic acid (TBA)
`at low pH, these reaction
`products
`form a pink
`chromophore
`that can be quantified
`by the change
`in absor-
`bance at 532 nm (A,,,).
`(final concn 0.0-10.0 mg/
`tyloxapol
`Normal
`saline
`(0.1 ml),
`ml), cetyl alcohol
`(final concn 0.0-10.0 mM), or Exosurf
`(final
`concn 0.0-10.0 mg/ml)
`was added
`to
`the
`reaction mixture.
`DPPC
`is not easily solubilized
`in aqueous buffer and therefore
`the American Physiological
`Society
`1217
`
`

`
`1218
`
`SURFACTANT,
`
`OXIDANTS,
`
`AND
`
`HYPEROXIC
`
`LUNG
`
`INJURY
`
`A A
`
`0.80
`
`E
`e
`g 0.60
`u7
`5
`Q) 0.40
`E
`tu
`a
`5 0.20
`co
`m a
`
`0.80 r,
`
`C
`
`0.80
`
`E
`c
`$ 0.60
`m
`5
`g 0.40
`c
`2
`: 0.20
`2
`u
`
`0.00
`
`0.1
`0.0
`Tyloxapol
`
`10.0
`
`1.0
`(mg/ml)
`
`0.1
`0.01
`0.0
`Cetyl Alcohol
`
`1.0
`(mM)
`
`1.
`
`10.0
`1.0
`0.1
`0.0
`(mg/ml)
`Exosurf
`of de-
`products
`acid-reactive
`thiobarbituric
`of
`.ibsorbance
`FIG.
`incubation
`of deoxyribose
`in an oxidant-gener-
`after
`in vitro
`oxyribose
`ating
`system
`with
`tyloxapol,
`cetyl
`alcohol,
`and Exosurf.
`Dose-depen-
`dent decreases
`in oxidized
`products
`of deoxyribose
`are evident
`with
`3 compounds.
`
`all
`
`reaction
`these studies. The
`in
`employed
`was not separately
`incubated
`or Exosurf, were
`mixtures, which
`included
`tyloxapol
`at 45OC for 30 min. To promote
`solubilization
`of cetyl alcohol,
`mixtures
`containing
`cetyl alcohol were
`incubated
`at 55°C.
`After
`incubation,
`the samples were centrifuged
`at 1,200
`g for 10
`min and 1.0 ml of both
`(wt/vol)
`TBA
`and 2.8% (wt/vol)
`1.0%
`trichloroacetic
`acid was added
`to 1.0 ml of supernatant.
`The
`samples were heated at 100°C
`for 10 min and cooled
`in ice, and
`the chromophore
`was determined
`in triplicate
`by its A532.
`Oxidant
`scavenging
`by tyloxapol,
`cetyl alcohol, and Exosurf
`was also measured by assay of hydroxylation
`products
`of salicy-
`late
`in vitro. Salicylic acid (2-hydroxybenzoic
`acid)
`reacts with
`hydroxyl
`radical
`to produce
`2,3- and 2,5-dihydroxybenzoic
`acid
`acids (9). The detection
`of 2,3- and 2,5-dihydroxybenzoic
`was performed
`using high-performance
`liquid
`chromatography
`(HPLC) with electrochemical
`detection
`(9). Suspensions
`of 10
`PM FeCl,,
`1.0 mM ascorbate, and 1.0 mM H,O, were employed
`to generate oxidants
`in the presence of 10.0 PM salicylate. Nor-
`mal saline
`(0.1 ml),
`tyloxapol
`(final concn 0.0-10.0 mg/ml),
`ce-
`tyl alcohol
`(final concn 0.0-10.0 mM), or Exosurf
`(final concn
`0.0-10.0 mg/ml) was added. The
`reaction mixtures were
`incu-
`bated at 45OC (except
`those with cetyl alcohol, which were incu-
`bated at 55°C)
`for 30 min and centrifuged
`at 1,200 g for 10 min.
`Supernatant
`was centrifuged
`(Beckman Microfuge
`E) through
`a 0.22~pm microfuge
`tube
`filter
`(no. 352-118,
`PGC Scientific)
`at
`15,000 g. A loo-p1 sample of the eluate was injected
`onto a C,,
`reverse-phase
`HPLC
`column
`(250 X 4.6 mm, Beckman
`no.
`235329). Hydroxylated
`products
`of salicylate were quantified
`with
`a Coulochem
`electrochemical
`detector
`(ESA model
`510OA), with
`the detector
`set at a reducing potential
`of -0.40 V
`direct current. The guard cell was set at an oxidizing
`potential
`of +0.40 V direct current
`(29). Measurements
`were done
`duplicate.
`to scavenge
`The
`in vitro capacity of tyloxapol
`l OH also was
`measured
`relative
`to that of salicylate.
`The
`reaction mixture
`included
`50 PM FeCl,, 50 PM EDTA,
`and 5.0 mM H,O,
`in phos-
`phate-buffered
`saline
`(pH 7.0). Salicylate was present at 5 mM
`(680 pg/ml).
`Tyloxapol
`was added
`in concentrations
`of 1.0,
`10.0, 100, 500, and 1,000 pg/ml. The solutions were
`irradiated
`using deuterium
`broad-band
`ultraviolet
`light
`for 2 min, and the
`reaction was then stopped with catalase
`(200 U). After precipi-
`tation of the protein with use of trichloroacetic
`acid and centrif-
`ugation, hydroxylated
`products
`of salicylate
`in the supernatant
`were quantified
`in duplicate
`by use of HPLC
`coupled with elec-
`trochemical
`detection.
`(273 t 16
`In vivo lung
`injury with 100% oxygen. Sixty-day-old
`(Charles
`g) specific pathogen-free
`male Sprague-Dawley
`rats
`with
`River, Wilmington,
`MA) were
`instilled
`intratracheally
`normal
`saline,
`tyloxapol
`(6.0 mg), tyloxapol
`(6.0 mg) plus cetyl
`alcohol
`(11.0 mg), or Exosurf
`(equivalent
`to 7.5 mg tyloxapol,
`11.3 mg cetyl alcohol,
`and 101.3 mg DPPC). All
`treatments
`were administered
`using an instillation
`volume of 0.5 ml. As a
`result of insolubility
`in aqueous buffers at body
`temperature,
`of
`cetyl alcohol alone was not tested, but rather a combination
`tyloxapol
`and cetyl alcohol was
`instilled
`in a ratio approxi-
`mately equal
`to that present
`in Exosurf. Rats were
`then ex-
`posed
`to air
`(n = 40) or 100% oxygen
`(n = 40)
`in Plexiglas
`chambers
`that were
`flushed with gas at a flow rate of 10 l/min.
`Oxygen
`percentage
`was
`continuously
`monitored
`in
`the
`chambers
`by a polarographic
`analyzer
`(Servomex,
`Sybron,
`Norwood,
`MA)
`and maintained
`at >98%. CO,
`levels were
`~0.5%. Temperature
`was kept between
`20 and 22°C. Food
`(Ralston Purina,
`St. Louis, MO) and water were available
`ad
`libitum. After 61 h of exposure, animals were killed with pento-
`barbital
`sodium
`(100 mg/kg
`ip; Abbott
`Laboratories,
`North
`Chicago,
`IL). Lung wet-to-dry
`weight
`ratios were calculated
`after
`tissue samples were dried
`for 96 h at 60°C. Pleural
`fluid
`
`in
`
`the chest cavity
`from
`fluid
`by aspirating
`volume was measured
`In some animals
`the
`in the diaphragm.
`through
`a small
`incision
`and 2% glutaraldehyde
`in 84 mM so-
`trachea was cannulated,
`dium cacodylate
`buffer at pH 7.4 was
`instilled
`at a constant
`pressure
`of 20 cmH,O. Tissue was examined
`by light micros-
`copy after
`it was sectioned
`and then stained with hematoxylin
`and eosin.
`TBA-reactive
`
`products
`
`in lung
`
`tissue are measured
`
`easily as
`
`Page 2
`
`

`
`SURFACTANT,
`
`OXIDANTS,
`
`AND
`
`HYPEROXIC
`
`LUNG
`
`INJURY
`
`1219
`
`0 2,5 Dihydroxybenzoic
`n 2,3 Dihydroxybenzoic
`
`Acid
`Acid
`
`K
`9.0
`8.0
`z
`7.0 -
`=
`P
`a 6.0 -
`z
`i
`k
`Q) z
`5
`
`50- 4:o -
`3.0 -
`2.0 -
`LO-
`
`Normal
`Saline
`
`l)rloxapol
`O.lmg/ml
`
`Wloxapol
`l.Omg/ml
`
`‘I)rloxapol
`lO.Omg/ml
`
`Cetyl
`Alcohol
`
`Exosurf
`lO.Omg/ml
`
`incubation
`in vitro
`after
`of salicylate
`products
`2. Hydroxylated
`FIG.
`along with
`tyloxapol,
`system
`of salicylate
`in an oxidant-generating
`tyl alcohol,
`and Exosurf.
`All 3 compounds
`decreased
`hydroxylation
`salicylate.
`Decrements
`with
`tyloxapol
`were dose dependent.
`Significant
`differences
`in hydroxylated
`products
`were
`found
`between
`reaction
`mix-
`tures with
`normal
`saline and
`those with
`10.0 mg/ml
`tyloxapol,
`1.0 mM
`cetyl
`alcohol,
`and 10.0 mg/ml
`Exosurf.
`
`ce-
`of
`
`. T
`
`mo.0
`ts 90
`'z
`'
`Q, 5
`8.0
`70
`.g 6:o
`3 5.0
`
`40 '
`E
`.F 3.0
`$ 20 .
`g 1.0
`3 0.0
`
`ratios
`lung weight
`FIG. 3. Wet-to-dry
`sure of rats
`to 100% oxygen.
`Significant
`only between
`saline-
`and
`tyloxapol-treated
`
`expo-
`61 h of continuous
`after
`differences
`were demonstrated
`rats.
`
`of lipids occurs
`stress. Peroxidation
`of oxidant
`index
`a sensitive
`and
`in vivo
`to oxygen
`in vitro
`of tissue
`during
`exposure
`(10)
`(34), although
`also react with
`other oxidized
`tissue components
`TBA and
`lead to an overestimate
`of fatty peroxide
`formation.
`At the end of the experiments,
`g of lung tissue was excised
`-0.5
`and TBA-reactive
`products were measured
`as previously
`de-
`scribed
`(28).
`intra-
`instilled
`rats were
`studies. Sprague-Dawley
`Mortality
`(6.0 mg), ty-
`tracheally with 0.5 ml of normal
`saline,
`tyloxapol
`loxapol(6.0
`mg) plus cetyl alcohol
`(11.0 mg), or Exosurf
`(equiv-
`Il.3 mg cetyl alcohol, and 101.3 mg
`alent
`to 7.5 mg tyloxapol,
`to air (n = 48) or 100%
`DPPC). These
`rats were
`then exposed
`(n = 48). Cages were checked every 3 h after 60 h for
`oxygen
`dead animals,
`and the data were
`recorded
`as percent
`survival.
`Statistics.
`The
`salicylate
`hydroxylation
`experiments
`in a
`Fenton
`system were performed
`twice. All other experiments
`were performed
`th ree
`times. Data are expressed
`as means k
`SD. An analysis of variance was used to determine
`differences
`
`FIG. 4. Pleural
`to 100% oxygen.
`all other
`therapies.
`
`fluid accumulation
`There were
`significant
`
`61 h of continuous
`after
`differences
`between
`
`exposure
`saline and
`
`(6). When F ratios were significant,
`groups
`between multiple
`means were compared
`post hoc using Scheffe’s
`test. For mortal-
`ity studies, x2 values were calculated
`and used to analyze differ-
`ences
`in
`total
`survival
`(6). Significance
`was assumed
`at
`P < 0.05.
`
`RESULTS
`
`The synthetic surfactant and two of its components,
`tyloxapol and cetyl alcohol, diminished in vitro oxidation
`of deoxyribose, as reflected by the absorbance of TBA-
`reactive products (Fig. 1). These decrements in oxidant
`generation were dependent on the concentration of the
`compounds or the mixture. Post hoc tests demonstrated
`significant differences in absorbances between reaction
`mixtures with normal saline and those with 0.1, 1.0, and
`10.0 mg/ml tyloxapol. Also, 1.0 mM cetyl alcohol and 1.0
`and 10.0 mg/ml Exosurf were significantly different
`from
`control. The same three compounds diminished in vitro
`hydroxylation
`of salicylate in a Fenton system (Fig. 2).
`The decreases in hydroxylation
`of salicylate associated
`with tyloxapol also were concentration dependent. Ty-
`loxapol competed successfully with salicylate for
`l OH
`generated using FeCI,, H,O,, and ultraviolet
`light. At
`1,000 pg/ml of the detergent, hydroxylated products of
`salicylate were diminished by >99%. This indicates that
`tyloxapol, on a weight basis, is a more efficient
`. OH scav-
`enger than salicylate.
`After prolonged exposure to 100% oxygen, the lungs of
`rats develop a defect in the barrier function of the alveo-
`lar-capillary membrane characterized by pulmonary
`edema and large pleural effusions. Wet-to-dry weight ra-
`tios of lung tissue from rats exposed to air and treated
`with saline, tyloxapol,
`tyloxapol plus cetyl alcohol, or
`Exosurf demonstrated no differences (control = 4.78
`t
`0.31). Exposure to 100% oxygen elevated the wet-to-dry
`weight ratio (Fig. 3). Whereas wet-to-dry
`lung weight ra-
`tios in rats exposed to oxygen and treated with tyloxapol,
`tyloxapol plus cetyl alcohol, and Exosurf were lower,
`post hoc tests indicated
`that only tyloxapol decreased
`
`Page 3
`
`

`
`1220
`
`SURFACTANT,
`
`OXIDANTS,
`
`AND
`
`HYPEROXIC
`
`LUNG
`
`INJURY
`
`\ 1
`
`.
`
`.?,
`
`Page 4
`
`

`
`SURFACTANT,
`
`OXIDANTS,
`
`AND
`
`HYPEROXIC
`
`LUNG
`
`INJURY
`
`1221
`
`-r
`
`T
`
`0.10
`E 0.09
`z
`0.08
`z
`0.07
`5 0.06
`0) 0.05
`0
`g
`0.04
`=p 0.03
`0 cn 0.02
`n
`a 0.01
`0.00
`
`of TBA-reactive
`FIG. 6. Absorbance
`to 100% oxygen.
`continuous
`exposure
`post
`hoc
`testing
`were
`significant
`only
`treated
`rats.
`
`products
`Differences
`between
`
`lung
`of
`between
`saline-
`
`after 61 h of
`values with
`and Exosurf-
`
`wet-to-dry weight ratios significantly compared with sa-
`line treatment.
`No pl .eural fluid was detected in rats exposed to air and
`treated with saline, tyloxapol,
`tyl oxapol plus cetyl alco-
`hol, or Exosurf. Animals exposed to 100% oxygen accu-
`mulated large quantities of pleural fluid (Fig. 4), and post
`hoc tests demonstrated significantly greater fluid in sa-
`line-treated oxygen-exposed animals than
`in animals
`given all other treatments. Despite the improvements
`in
`several indexes of injury after treatment with Exosurf or
`its components, histological findings typical of hyperoxic
`lung injury were observed after all therapies (Fig. 5).
`No differences were demonstrated among TBA-reac-
`tive products of rat lung exposed to air and treated with
`saline, tyloxapol,
`tyloxapol plus cetyl alcohol, and Exo-
`surf (A,,, = 0.051 t 0.004). Concentrations of TBA-reac-
`tive products were significantly elevated in lungs of rats
`exposed to oxygen (Fig. 6). Whereas all values in rats
`
`There were no deaths among animals treated with the
`test compounds and exposed to air. In rats the mean
`survival during continuous exposure to 100% oxygen at
`sea level is 60-66 h (7). Mean survival in rats treated with
`saline and exposed to 100% oxygen was 67.3
`t 8.1 h (Fig.
`7). Treatments with tyloxapol,
`tyloxapol plus cetyl alco-
`hol, and Exosurf significantly
`increased survival through
`96 h. There was no significant difference in survival at 96
`h between Exosurf-treated
`rats and animals instilled
`with tyloxapol plus cetyl alcohol.
`
`DISCUSSION
`
`radicals are produced as normal by-
`Oxygen-derived
`products of metabolism. These oxidants are scavenged
`by antioxidant enzymes (i.e., superoxide dismutases, ca-
`talase, and glutathione peroxidase) and molecular scav-
`,&carotene, and
`engers (i.e. 9 glutathione, a-tocopherol,
`
`ascorbic acid). During exposure to hyperoxia, an in-
`creased rate of radical generation
`is assumed to over-
`whelm endogenous antioxidant defenses (11, 14). These
`reactive oxygen species can cause cellular
`injury and
`death through lipid peroxidation, protein oxidation, sulf-
`hydryl depletion, and DNA damage. The major source of
`pulmonary oxidant stress during hyperoxia is likely to be
`increased cellular production of 0, and H,O,. Whereas
`both oxidant species may have deleterious effects on bio-
`logical materials directly, some portion of their toxicity
`may be mediated through an iron-catalyzed generation of
`l OH with 0, as the necessary reductant and H,O, as the
`substrate (2, 14). The hydroxyl
`radical scavenger di-
`methylthiourea and the iron chelator deferoxamine de-
`crease hyperoxic
`injury
`in an animal model. Conse-
`quently,
`the oxidant-generating
`system that we selected
`to test for in vitro antioxidant activity of Exosurf and its
`components was one that produced hydroxyl
`radical. Ex-
`osurf functioned as an antioxidant
`in this in vitro system.
`Surfactant-enriched material has a capacity to be oxi-
`dized (12,32). The components of Exosurf were tested in
`vitro, except for DPPC, which is poorly water soluble and
`chemically the least likely component to react with oxy-
`gen-derived radicals. The alcohol and detergent compo-
`nents actively contributed
`to the antioxidant properties
`of the mixture. To scavenge radicals, these compounds
`must be easily oxidized
`to stable chemical forms. Alco-
`hols are well recognized as antioxidants and are oxidized
`to aldehydes (4). Some detergents have been observed to
`stimulate oxidant generation
`in vitro
`in acellular
`(30)
`and cell ular systems (19). The exact mechanisms for the
`in vitro antioxidant activity of the nonionic detergent
`and the products of its oxidation are not known. Tyloxa-
`pol is an alkylaryl polyether alcohol polymer synthesized
`from the reaction of 4-(1,1,3,3-tetramethylbutyl)phenol
`with
`formaldehyde and oxirane.
`It retains
`functional
`
`100
`
`80
`
`ii l : 60
`‘3
`cn
`
`Q)
`e
`
`20
`
`0
`
`’
`0
`
`I
`24
`
`I
`48
`
`I
`72
`
`96
`
`Hours of Exposure
`to 100% oxygen
`after
`continuously
`exposed
`of rats
`7. Survival
`FIG.
`alcohol
`tyloxapol
`(m),
`tyloxapol
`plus
`cetyl
`with
`saline
`(o),
`treatment
`tyloxa-
`to saline,
`therapies
`with
`tyloxapol,
`(A), or Exosurf
`(+). Relative
`survival.
`pol plus
`cetyl
`alcohol,
`and Exosurf
`significantly
`improved
`Among
`the 3 therapies,
`mortality
`after
`treatment
`with
`tyloxapol
`plus
`cetyl
`alcohol
`was significantly
`than
`that
`after
`tyloxapol
`alone.
`
`less
`
`Page 5
`
`

`
`1222
`
`SURFACTANT,
`
`OXIDANTS,
`
`AND
`
`HYPEROXIC
`
`LUNG
`
`INJURY
`
`technical
`for
`John Patterson
`thank
`We
`son
`for preparation
`of the manuscript.
`Heart,
`by National
`This
`work
`was
`supported
`in part
`Blood
`Institute
`Grants
`HL-31992,
`HL-02655,
`and HL-32188.
`Address
`for
`reprint
`requests:
`A. J. Ghio, Box 3177, Duke University
`Medical
`Center,
`Durham,
`NC 27710
`
`assistance
`
`and Louise Wil-
`
`Lung,
`
`and
`
`Received
`
`7 September
`
`1993; accepted
`
`in
`
`final
`
`form
`
`8 April
`
`1994.
`
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`in the lung. This ele-
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`tioxidant
`properties
`conferred
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`by light microscopy
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`changes
`induced
`by hyperoxia.
`to 100% oxygen at one atmo-
`exposure
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`sphere causes death
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`species and is a
`contributing
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`severe
`lung
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`plus
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`surfactant
`a
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`against
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`the 1950s with
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`(3). Alevaire
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`

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`
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`
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`LUNG
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`INJURY
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