Lipid compositional analysis of pulmonary surfactant monolayers and monolayer-associated reservoirs

Pulmonary surfactant is a lipid:protein complex containing dipalmitoyl-phosphatidylcholine (DPPC) as the major component. Recent studies indicate adsorbed surfactant films consist of a surface monolayer and a monolayer-associated reservoir. It has been hypothesized that the monolayer and its functionally contiguous reservoir may be enriched in DPPC relative to bulk phase surfactant. We investigated the compositional relationship between the monolayer and its reservoir using paper-supported wet bridges to transfer films from adsorbing dishes to clean surfaces on spreading dishes. Spreading films appear to form monolayers in the spreading dishes. We employed bovine lipid extract surfactant [BLES(chol)] containing [3H]DPPC and either [14C]palmitoyl, oleoyl-phosphatidylcholine (POPC), [14C]dipalmitoyl-phosphatidylglycerol (DPPG), [14C]palmitoyl, oleoyl-phosphatidylglycerol (POPG), or [14C]cholesterol. Radiolabeled phosphatidylglycerols were prepared using phospholipase D. The studies demonstrated that the [3H]DPPC-[14C] POPC ratios were the same in the prepared BLES dispersions as in Langmuir-Blodgett films, indicating a lack of DPPC selectivity during film formation. Furthermore, identical 3H-14C isotopic ratios were observed with DPPC and either 14C-labeled POPC, DPPG, POPG, or cholesterol in the original dispersions, the bulk phases in adsorption dish D1, and monolayers recovered from spreading dish D2. These relationships remained unperturbed with 2-fold increases in bulk concentrations in D1 and 10-fold variations in D1-D2 surface area.These results indicate adsorbed surfactant monolayers and their associated reservoirs possess similar lipid compositions and argue against selective adsorption of DPPC. Pulmonary surfactant is a lipid:protein complex containing dipalmitoyl-phosphatidylcholine (DPPC) as the major component. Recent studies indicate adsorbed surfactant films consist of a surface monolayer and a monolayer-associated reservoir. It has been hypothesized that the monolayer and its functionally contiguous reservoir may be enriched in DPPC relative to bulk phase surfactant. We investigated the compositional relationship between the monolayer and its reservoir using paper-supported wet bridges to transfer films from adsorbing dishes to clean surfaces on spreading dishes. Spreading films appear to form monolayers in the spreading dishes. We employed bovine lipid extract surfactant [BLES(chol)] containing [3H]DPPC and either [14C]palmitoyl, oleoyl-phosphatidylcholine (POPC), [14C]dipalmitoyl-phosphatidylglycerol (DPPG), [14C]palmitoyl, oleoyl-phosphatidylglycerol (POPG), or [14C]cholesterol. Radiolabeled phosphatidylglycerols were prepared using phospholipase D. The studies demonstrated that the [3H]DPPC-[14C] POPC ratios were the same in the prepared BLES dispersions as in Langmuir-Blodgett films, indicating a lack of DPPC selectivity during film formation. Furthermore, identical 3H-14C isotopic ratios were observed with DPPC and either 14C-labeled POPC, DPPG, POPG, or cholesterol in the original dispersions, the bulk phases in adsorption dish D1, and monolayers recovered from spreading dish D2. These relationships remained unperturbed with 2-fold increases in bulk concentrations in D1 and 10-fold variations in D1-D2 surface area. These results indicate adsorbed surfactant monolayers and their associated reservoirs possess similar lipid compositions and argue against selective adsorption of DPPC. It is generally agreed that the alveolar surface is covered by a continuous thin layer of water that supports a surface active film of pulmonary surfactant (1Bastacky J. Lee C.Y. Goerke J. Koushafar J.H. Yager D. Kenaga L. Speed T.P. Chen Y. Clements J.A. Alveolar lining layer is thin and continuous: low-temperature scanning electron microscopy of rat lung.J. Appl. Physiol. 1995; 79: 1615-1628Google Scholar, 2Manabe T. Freeze-fracture study of alveolar lining layer in adult rat lung homogenates.J. Ultrastruct. Res. 1979; 69: 86-97Google Scholar) [for review see (3Goerke J. Pulmonary surfactant: Functions and molecular composition.Biochim. Biophys. Acta. 1998; 1408: 79-89Google Scholar, 4Perez-Gil J. Keough K.M.W. Interfacial properties of surfactant proteins.Biochim. Biophys. Acta. 1998; 1408: 203-217Google Scholar, 5Possmayer F. Physicochemical aspects of pulmonary surfactant.in: Polin R.A. Fox W.W. Fetal and Neonatal Physiology. W. B. Saunders Company, Philadelphia, PA1997: 1259-1275Google Scholar, 6Possmayer F. Nag K. Rodriguez K. Qanbar R. Schürch S. Surface activity in vitro: role of surfactant proteins.Comp. Biochem. Physiol. A Mol. Integr. Physiol. 2001; 129: 209-220Google Scholar, 7Veldhuizen R. Nag K. Orgeig S. Possmayer F. The role of lipids in pulmonary surfactant.Biochim. Biophys. Acta. 1998; 1408: 90-108Google Scholar)]. Through its ability to reduce the surface tension of this air-water interface, pulmonary surfactant stabilizes the terminal air spaces. Considerable evidence has accumulated indicating that surfactant films are composed of more than a single monolayer. Pattle (8Pattle R. Properties, function and origin of the alveolar lining layer.Nature. 1955; 175: 1125-1126Google Scholar) first proposed that the surfactant film overlying the alveolar lining layer consists of a monomolecular layer and underlying material that serves as a reservoir. Using electron microscopy, Weibel and Gil (9Weibel E.R. Gil J. Electron microscopic demonstration of an extracellular duplex lining layer of the alveoli.Resp. Physiol. 1968; 4: 42-57Google Scholar) observed the presence of lamellar layers of phospholipids with three to six repeating distances of 38–51 Å on the alveolar epithelial surface of rat lungs. Studies by Manabe (2Manabe T. Freeze-fracture study of alveolar lining layer in adult rat lung homogenates.J. Ultrastruct. Res. 1979; 69: 86-97Google Scholar) and, more recently, Bastacky et al. (1Bastacky J. Lee C.Y. Goerke J. Koushafar J.H. Yager D. Kenaga L. Speed T.P. Chen Y. Clements J.A. Alveolar lining layer is thin and continuous: low-temperature scanning electron microscopy of rat lung.J. Appl. Physiol. 1995; 79: 1615-1628Google Scholar) using scanning electron microscopic studies indicate that the alveolar lining layer is continuous and its surface contains many lipidic structures. In vitro studies involving surface films adsorbed from surfactant dispersions have also provided evidence indicating the surface monolayer is accompanied by a functional continuous reservoir (10Schürch S. Green F.H.Y. Bachofen H. Formation and structure of surface films: captive bubble surfactometry.Biochim. Biophys. Acta. 1998; 1408: 180-202Google Scholar, 11Schürch S. Bachofen H. Biophysical aspects in the design of therapeutic surfactant.in: Robertson B. Taeusch H.W. Surfactant Therapy for Lung Disease. Marcel Dekker, New Scholar, Possmayer F. of pulmonary surfactant A and lipid on and of in surface Res. Scholar, Possmayer F. and cholesterol in monolayers from adsorbed films of pulmonary Res. 2001; Surfactant reservoirs that phospholipids to the air-water during surface also be during film A scanning and microscopy study of the structure and function of a pulmonary Biophys. J. Scholar, S. T. Surfactant A of from alveolar J. Physiol. Scholar, Lee J.A. of lung surfactant with J. 2001; Scholar, of surfactant monolayers on as as lipid microscopy Scholar) in of pulmonary surfactant in surface film and Biophys. Acta. Scholar, J.A. J. F. The and of lung 2001; Scholar)]. Pulmonary surfactant consists of lipids and The of bovine pulmonary is of consists of of and and S. Possmayer F. pulmonary surfactant: and (DPPC) and are major molecular and are S. Possmayer F. pulmonary surfactant: and Scholar, molecular of lung J. Physiol. 1995; Scholar, A of the molecular compositions of lung surfactant Biochem. Physiol. A Mol. Integr. Physiol. 2001; 129: pulmonary surfactant also contains of is Pulmonary surfactant consist of and and complex and and of surfactant Biophys. Acta. 1998; 1408: Scholar, and Biochem. Physiol. A Mol. Integr. Physiol. 2001; 129: Scholar, S. F. and properties of surfactant Biophys. Acta. 1998; 1408: Scholar, J. and properties of surfactant Biophys. Acta. 1998; 1408: Scholar, and properties of surfactant Biophys. Acta. 1998; 1408: Scholar, of surfactant and Physiol. 2001; The adsorption of surfactant to the surface to form films is for and lung function review for Scholar, Pulmonary surfactant: and the of pulmonary a of and an B. and the functional of lipids in Biophys. Acta. 1979; Scholar, B. S. and the of 1998; that the ability of DPPC to surface of to These properties monolayers of DPPC to reduce surface tension to on the surface monolayers of phospholipids the surface tension of (3Goerke J. Pulmonary surfactant: Functions and molecular composition.Biochim. Biophys. Acta. 1998; 1408: 79-89Google Scholar, 5Possmayer F. Physicochemical aspects of pulmonary surfactant.in: Polin R.A. Fox W.W. Fetal and Neonatal Physiology. W. B. Saunders Company, Philadelphia, PA1997: 1259-1275Google Scholar, 6Possmayer F. Nag K. Rodriguez K. Qanbar R. Schürch S. Surface activity in vitro: role of surfactant proteins.Comp. Biochem. Physiol. A Mol. Integr. Physiol. 2001; 129: 209-220Google Scholar, Pulmonary surfactant: and Scholar, J. Lung surfactant.Biochim. Biophys. Acta. of DPPC and lipid extract the surfactant appear for adsorption of DPPC the surface The ability of surfactant films to surface tension during (8Pattle R. Properties, function and origin of the alveolar lining layer.Nature. 1955; 175: 1125-1126Google Scholar, J. Surface tension of lung Scholar, Goerke J. Clements J.A. Pulmonary surface film and Appl. Physiol. 1979; Scholar, J. J. of monolayer Appl. Physiol. Scholar) has been to the of a monolayer enriched in DPPC in (3Goerke J. Pulmonary surfactant: Functions and molecular composition.Biochim. Biophys. Acta. 1998; 1408: 79-89Google Scholar, 4Perez-Gil J. Keough K.M.W. Interfacial properties of surfactant proteins.Biochim. Biophys. Acta. 1998; 1408: 203-217Google Scholar, 5Possmayer F. Physicochemical aspects of pulmonary surfactant.in: Polin R.A. Fox W.W. Fetal and Neonatal Physiology. W. B. Saunders Company, Philadelphia, PA1997: 1259-1275Google Scholar, 6Possmayer F. Nag K. Rodriguez K. Qanbar R. Schürch S. Surface activity in vitro: role of surfactant proteins.Comp. Biochem. Physiol. A Mol. Integr. Physiol. 2001; 129: 209-220Google Scholar, J. Lung surfactant.Biochim. Biophys. Acta. Scholar, S. Qanbar R. Bachofen H. Possmayer F. The surfactant reservoir in the alveolar 1995; Scholar, S. Bachofen H. Possmayer F. Surface activity in in and in the captive bubble Biochem. Physiol. A Mol. Integr. Physiol. 2001; 129: Scholar)]. It has been that DPPC during film of the more lipids The properties of an lung surfactant.Biochim. Biophys. Acta. 1979; Scholar, J.A. Functions of the alveolar Scholar, The surface properties of to of lung Biophys. Acta. 1968; during in monolayers enriched in DPPC by this The presence of a surface monolayer enriched in DPPC is with the properties of lung T. J. and of lung.J. Appl. Physiol. Recent have demonstrated that surface to surface during film of adsorbed surfactant films be than that by the DPPC of surfactant S. Qanbar R. Bachofen H. Possmayer F. The surfactant reservoir in the alveolar 1995; Scholar, S. Bachofen H. Goerke J. Possmayer F. A captive bubble the in of lung surfactant Appl. Physiol. Scholar, R. S. Possmayer F. Schürch S. of the of in surfactant film and J. Physiol. Scholar, K. K. Schürch S. Possmayer F. of pulmonary surfactant J. Physiol. Scholar, K. Nag K. Schürch S. Possmayer F. Surfactant with and J. Physiol. Lung Mol. Physiol. 2001; These to the that the surface monolayer may enriched in DPPC during adsorption (3Goerke J. Pulmonary surfactant: Functions and molecular composition.Biochim. Biophys. Acta. 1998; 1408: 79-89Google Scholar, 4Perez-Gil J. Keough K.M.W. Interfacial properties of surfactant proteins.Biochim. Biophys. Acta. 1998; 1408: 203-217Google Scholar, 5Possmayer F. Physicochemical aspects of pulmonary surfactant.in: Polin R.A. Fox W.W. Fetal and Neonatal Physiology. W. B. Saunders Company, Philadelphia, PA1997: 1259-1275Google Scholar, 6Possmayer F. Nag K. Rodriguez K. Qanbar R. Schürch S. Surface activity in vitro: role of surfactant proteins.Comp. Biochem. Physiol. A Mol. Integr. Physiol. 2001; 129: 209-220Google Scholar, S. Qanbar R. Bachofen H. Possmayer F. The surfactant reservoir in the alveolar 1995; Scholar, S. Bachofen H. Possmayer F. Surface activity in in and in the captive bubble Biochem. Physiol. A Mol. Integr. Physiol. 2001; 129: We have a paper-supported wet and monolayer from a a film Scholar, H. and between lipid layers the surface of a Biophys. Acta. 1979; Scholar) to transfer lipid from the surface of adsorbing dishes containing surfactant dispersions to the surface of spreading dishes Possmayer F. and cholesterol in monolayers from adsorbed films of pulmonary Res. 2001; The of material in the films to lipid compositions evidence indicating and were the surface monolayer Possmayer F. and cholesterol in monolayers from adsorbed films of pulmonary Res. 2001; We also evidence indicating the underlying reservoir functionally contiguous with the surface monolayer. the lipid compositions of the adsorbed monolayer and its associated reservoir have been In the have [3H]DPPC and to the relative of in the bulk the surface and the reservoir. In and are were prepared and for similar [3H]DPPC and with the bovine surfactant extract were also results indicate that the [3H]DPPC of the adsorbed monolayers is enriched relative to the reservoir or lipid extract surfactant in the bulk and were from New prepared from a from D. R. and K. A from and were from of and were with a using water a in from bovine pulmonary provided by BLES by the of and A of lipid and J. Biochem. Physiol. as Possmayer F. of pulmonary surfactant A and lipid on and of in surface Res. lipid of surfactant and surfactant and or from has the lipids S. Possmayer F. pulmonary surfactant: and and were prepared from the by phospholipase using a of the of and The of and by Biophys. Acta. in with phospholipase in of and in the same The with a for the of as by using a by et al. Chen of phospholipids in thin layer The with of and the were with the of and A of lipid and J. Biochem. Physiol. The were by The with of The in were the and with a of The were with Radiolabeled by as The of with [3H]DPPC and either or in The and the with and The with a for and for were to a as a of the dish see the The of the [3H]DPPC and that of and dish and dish containing and in a water were with a of that with a A to surface The surface of D1 or and that of or surface ratios for D1-D2 of and of a of [3H]DPPC and or The of in D1 for D1-D2 for D1-D2 and for D1-D2 The the surface tension in were in a The surface monolayer in with a a and lipids were with A of lipid and J. Biochem. Physiol. The layer to a and of the from the bulk were and to a the of of and the of were from the to of films were from adsorbed dispersions of and on as Possmayer F. of pulmonary surfactant A and lipid on and of in surface Res. Surface tension during The films were with a and the were in of were from investigated the transfer of from the bulk phase to the air-water during films were from dispersions of and that the films DPPC to POPC ratios similar to in the dispersions and in recovered from the bulk In have observed that the films in this more than from a single monolayer Possmayer F. of pulmonary surfactant A and lipid on and of in surface Res. In the presence of lipid These that films prepared from adsorbed films the surface monolayer and associated The indicate that the relative concentrations of DPPC and POPC in the adsorbed films are same as in the bulk phase and are of the original isotopic ratios in films from [3H]DPPC and dispersions of and to adsorbing dish were prepared and films were with and by of phase were from the of the adsorbing dish of the of and to adsorbing dish were prepared and films were with and by phase were from the of the adsorbing dish of the in a ratios in surface films recovered from spreading dish that of BLES dispersions adsorbing dish surface D1 the 3H-14C ratios of the recovered surfactant were a of that of the original and of recovered from the bulk phase of D1 surface tension been is the of the These results that POPC is adsorbed the surface film with DPPC. It is also that the relative concentrations of DPPC and POPC in the films to are similar to of the in the adsorption dish D1 of ratios in monolayers in from adsorbed films of [3H]DPPC and D1 and BLES in the bulk phase of of D1-D2 dispersions are and adsorbing dish were prepared and from adsorbed films were and with of were from the of D1 the bridges between D1 and of are are of D1-D2 dispersions are and adsorbing dish were prepared and from adsorbed films were and with of were from the of D1 the bridges between D1 and of are are dispersions are and adsorbing dish were prepared and from adsorbed films were and with were from the of D1 the bridges between D1 and are in a The in were from films in spreading dish that the surface of to the D1 the ratios were to the and recovered from the bulk These results that the relative of DPPC and POPC in films in spreading dish as surfactant material is the wet is in pulmonary and this lipid surface during S. Keough Pulmonary surfactant and in monolayers the air-water of pulmonary surfactant and J. prepared using to the of on adsorption surface to the results on DPPC and POPC identical 3H-14C ratios were observed in films recovered from spreading dish as in the original dispersions and in recovered from the bulk phase of adsorbing dish D1 The remained of the D1-D2 surface or These results that is adsorbed surface films with DPPC and that the relative concentrations of phase phospholipids to spreading dish to in the original ratios in bulk and of D1-D2 of of of D1-D2 of of were as in in a were as in The of using prepared The in ratios in films from spreading dish were identical to the isotopic ratios in the original dispersions and in recovered from the of adsorbing dish The remained of the films were from adsorbing surfaces or the surface of spreading dish D2. the relative concentrations of DPPC and in the films to remained a of adsorbing to spreading surface and a in surfactant bulk ratios in bulk and of D1-D2 of of of D1-D2 of of of D1-D2 of of were as in in a were as in its role cholesterol is in in and in from and R. Nag K. Orgeig S. Possmayer F. The role of lipids in pulmonary surfactant.Biochim. Biophys. Acta. 1998; 1408: 90-108Google Scholar, S. The of cholesterol in pulmonary surfactant: from and Biochem. Physiol. A Mol. Integr. Physiol. 2001; 129: We evidence indicating cholesterol adsorbed with DPPC the surface monolayers from Possmayer F. and cholesterol in monolayers from adsorbed films of pulmonary Res. 2001; The results in are in that is adsorbed the surface films with The 3H-14C ratios in films to spreading dish were identical to in the and to of recovered from the of results were the films were from surfaces with or the of the spreading dish D2. These results cholesterol is adsorbed with DPPC surface films and indicate lipids to DPPC and to ratios in bulk and of D1-D2 of of of D1-D2 of of were as in in a were as in pulmonary are in and DPPC is the major of surfactant that surface during monolayer (3Goerke J. Pulmonary surfactant: Functions and molecular composition.Biochim. Biophys. Acta. 1998; 1408: 79-89Google Scholar, 4Perez-Gil J. Keough K.M.W. Interfacial properties of surfactant proteins.Biochim. Biophys. Acta. 1998; 1408: 203-217Google Scholar, 5Possmayer F. Physicochemical aspects of pulmonary surfactant.in: Polin R.A. Fox W.W. Fetal and Neonatal Physiology. W. B. Saunders Company, Philadelphia, PA1997: 1259-1275Google Scholar, 6Possmayer F. Nag K. Rodriguez K. Qanbar R. Schürch S. Surface activity in vitro: role of surfactant proteins.Comp. Biochem. Physiol. A Mol. Integr. Physiol. 2001; 129: 209-220Google Scholar, 7Veldhuizen R. Nag K. Orgeig S. Possmayer F. The role of lipids in pulmonary surfactant.Biochim. Biophys. Acta. 1998; 1408: 90-108Google Scholar, J. Lung surfactant.Biochim. Biophys. Acta. The generally for surfactant function that the lung is by an monolayer that is enriched in DPPC Goerke J. Clements J.A. Pulmonary surface film and Appl. Physiol. 1979; Scholar, The properties of an lung surfactant.Biochim. Biophys. Acta. 1979; Scholar, J.A. Functions of the alveolar Scholar, The surface properties of to of lung Biophys. Acta. 1968; The for DPPC that adsorbed surfactant monolayers the bulk during the more are of the surface monolayer. The DPPC is in for the monolayer to the surface to the a of studies have demonstrated that surface tension be with surface than be by the S. Bachofen H. Goerke J. Possmayer F. A captive bubble the in of lung surfactant Appl. Physiol. Scholar, R. S. Possmayer F. Schürch S. of the of in surfactant film and J. Physiol. Scholar, K. K. Schürch S. Possmayer F. of pulmonary surfactant J. Physiol. Scholar, K. Nag K. Schürch S. Possmayer F. Surfactant with and J. Physiol. Lung Mol. Physiol. 2001; It has been proposed that or of surfactant lipids during adsorption as to a monolayer enriched in DPPC (3Goerke J. Pulmonary surfactant: Functions and molecular composition.Biochim. Biophys. Acta. 1998; 1408: 79-89Google Scholar, 4Perez-Gil J. Keough K.M.W. Interfacial properties of surfactant proteins.Biochim. Biophys. Acta. 1998; 1408: 203-217Google Scholar, 5Possmayer F. Physicochemical aspects of pulmonary surfactant.in: Polin R.A. Fox W.W. Fetal and Neonatal Physiology. W. B. Saunders Company, Philadelphia, PA1997: 1259-1275Google Scholar, 6Possmayer F. Nag K. Rodriguez K. Qanbar R. Schürch S. Surface activity in vitro: role of surfactant proteins.Comp. Biochem. Physiol. A Mol. Integr. Physiol. 2001; 129: 209-220Google Scholar, 7Veldhuizen R. Nag K. Orgeig S. Possmayer F. The role of lipids in pulmonary surfactant.Biochim. Biophys. Acta. 1998; 1408: 90-108Google Scholar, S. Qanbar R. Bachofen H. Possmayer F. The surfactant reservoir in the alveolar 1995; Scholar, S. Bachofen H. Possmayer F. Surface activity in in and in the captive bubble Biochem. Physiol. A Mol. Integr. Physiol. 2001; 129: Recent results from have the alveolar a monolayer. et al. have and microscopy to that the from lung surfactant surface monolayer in DPPC B. between phase of lung surfactant phospholipids and the of surfactant J. 2001; In et al. have observed that monolayers of or POPC were to in the lung alveolar surface from to be of phase in monolayers surface J. Scholar, monolayers of pulmonary J. 2001; Scholar, J. of monolayers the air-water J. films surface for These that surfactant monolayers surface surface surface of their In with have observed that a in of films from monolayers of surface of the cholesterol is a of the surface monolayer or is associated with the reservoir from studies Possmayer F. of pulmonary surfactant A with and cholesterol the Res. 1998; We have film by BLES the of dishes and surface tension with a Surface with a the water surface Possmayer F. of pulmonary surfactant A and lipid on and of in surface Res. Scholar, Possmayer F. of pulmonary surfactant A with and cholesterol the Res. 1998; have a in water of the surface in the surface the surface In the surfactant for of a single monolayer. and adsorbed and the surface tension of in and Surface from or BLES more as the of surface in three surface The in and the of were with a in surface with the phospholipids to form a film that to the a surface of surfactant concentrations in the bulk It has been that surfactant and on an surface as and properties of lung The is with studies with that this therapeutic surfactant in S. D. T. Robertson B. Surface activity of lipid extract surfactant in to film and Appl. Physiol. studies using the the for surface tension in adsorbing dish D1 were similar to in the Possmayer F. and cholesterol in monolayers from adsorbed films of pulmonary Res. 2001; in the of the studies adsorbing dishes were the were These are with the that of the surfactant film in dish D1 the for spreading of the surfactant film the wet the surface of dish D2. In the have investigated surfactant film by a paper-supported wet to transfer surfactant films from the surface of an adsorbing D1, to the surface of a spreading D2. the of lipid to the spreading dish are the surface tension of [3H]DPPC in with lipids to the relative concentrations of surfactant in the dispersions and surface Using this observed the of films on identical to that of the original studies have that films the surface monolayer and associated material Possmayer F. of pulmonary surfactant A and lipid on and of in surface Res. Scholar, Possmayer F. and cholesterol in monolayers from adsorbed films of pulmonary Res. 2001; Scholar, Possmayer F. of pulmonary surfactant with monolayers of and of Res. films surfactant material of the surfactant material associated with surfactant monolayers as a functional reservoir is this that is selectivity for DPPC surface films during The to the relative compositions of surface films from the adsorbing D1, to the spreading by a thin paper-supported wet have that a in the surface of of the wet increases in surface These and by and are with the film in a monolayer Possmayer F. and cholesterol in monolayers from adsorbed films of pulmonary Res. 2001; Scholar, and monolayer from a a film Scholar, H. and between lipid layers the surface of a Biophys. Acta. 1979; as the film is from a of surface in D1 to a surface in a single monolayer. Surfactant material from the reservoir in D1 to the surface monolayer and serves to lipid transfer the wet surface tension is The to study relative transfer of the surface in adsorbing dish D1 to films on the surface of D2. It observed that the 3H-14C of the film identical to the isotopic of the dispersions and of recovered from the of with the studies this indicate that similar relative concentrations were during of the surface film and its transfer the Furthermore, this relationship a of concentrations of with in The same relationship for films in with relative surface for D1 and from to These results a lack of DPPC selectivity POPC in surface film and results were in studies relative 3H-14C with [3H]DPPC and or that lipids to during adsorption and The on the surface origin monolayer or of the material to the spreading in It is that in the surface of D1 of the monolayer to be from the original adsorbed and from the monolayer-associated reservoir in film spreading of reservoir surfactant the surface monolayers in a the monolayer spreading dish from the original adsorbed monolayer and an of the monolayer in D1 from its reservoir. Considerable evidence reservoir is on surfactant bulk F. Nag K. Rodriguez K. Qanbar R. Schürch S. Surface activity in vitro: role of surfactant proteins.Comp. Biochem. Physiol. A Mol. Integr. Physiol. 2001; 129: 209-220Google Scholar, S. Green F.H.Y. Bachofen H. Formation and structure of surface films: captive bubble surfactometry.Biochim. Biophys. Acta. 1998; 1408: 180-202Google Scholar, S. Qanbar R. Bachofen H. Possmayer F. The surfactant reservoir in the alveolar 1995; The that surfactant bulk from to the lipid isotopic in is with identical relative concentrations for phospholipids in the bulk adsorbed monolayer and the reservoir in The for were that surface tension in the spreading dish of the in These were in to the of surface to of in the results were the monolayers were to for or more surface tension with surface D1 the film spreading from the monolayer in surface D1-D2 the of monolayer in D1 from the original adsorbed monolayer in dish D1 with surfactant D1-D2 of the monolayer in from reservoir material in reservoir material to associated with the adsorbed monolayer in the in surface investigated with the results with lipid were The of the lipid with the BLES of the evidence against relative increases in DPPC of the original adsorbed monolayer. The on relative of the surface It is that and adsorbed films containing phase phospholipids form enriched in DPPC B. between phase of lung surfactant phospholipids and the of surfactant J. 2001; Scholar, D. R. microscopy the air-water of an air bubble with pulmonary J. Scholar, D. R. microscopy of pulmonary surfactant the air-water of an air bubble of J. Scholar, K. J. J. Keough in films of lung surfactant the air-water J. 1998; Scholar) in J.A. J. F. The and of lung 2001; Scholar)]. are and appear the surface of the film and the relative of lipid ratios selective transfer of be as an in 3H-14C against transfer appear as a in this The lack of argue against selectivity in lipid transfer to lipid In studies have the relationship between the lipid of adsorbed monolayers and their associated reservoirs and to the lipid of the lipid extract surfactant the bulk The relative concentrations of [3H]DPPC and 14C-labeled POPC, DPPG, and were to the of and on DPPC selective to the of lipid The the of bulk surfactant concentrations of to surfactant has a major on surface activity and reservoir formation. These also the of the relative surface of adsorbing D1 to the spreading dishes by and, in the of POPG, The studies a lack of lipid selectivity in the of surface films during to evidence for DPPC during of adsorbed These results are to the that lipid during surfactant monolayer formation. are with evidence against the has proposed that the ability of pulmonary surfactant to surface is on monolayers enriched in DPPC. by a to the of in Fetal and Neonatal and from the The BLES for bovine surfactant. The also D. R. and K. for of phospholipase D.

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