Surfactant in newborn compared with adolescent pigs: Adaptation to neonatal respiration

Surfactant composition and function differ between vertebrates, depending on pulmonary anatomy and respiratory physiology. Because pulmonary development in pigs is similar to that in humans, we investigated surface tension function, composition of phospholipid molecular species, and concentrations of surfactant protein (SP)-A to -D in term newborn pigs (NP) compared with adolescent pigs (AP), using the pulsating bubble surfactometer, mass spectrometry, high-performance liquid chromatography, and immunoblot techniques (IT). NP was more potent than AP surfactant in reaching minimal surface tension values near zero mN/m. Whereas SP-A and SP-D were comparable, SP-B and SP-C were increased 3- to 4-fold in NP surfactant. Moreover, fluidizing phospholipids such as palmitoylmyristoyl-PC (PC16:0/14:0) and palmitoylpalmitoleoyl-PC (PC16: 0/16:1) were increased at the expense of PC16:0/16:0 (32.4 ± 0.6 versus 44.5 ± 3.2%, respectively). Whereas concentrations of total anionic phospholipids were similar in NP and AP surfactant (9.9 ± 0.3 and 12.0 ± 0.3%, respectively), phosphatidylinositol was the predominant anionic phospholipid in NP surfactant. We conclude that, compared with AP, NP surfactant displays better surface tension function under dynamic conditions, which is associated with increased concentrations of SP-B and SP-C, as well as fluidizing phospholipids at the expense of PC16:0/16:0

Pulmonary surfactant in birds: coping with surface tension in a tubular lung

As birds have tubular lungs that do not contain alveoli, avian surfactant predominantly functions to maintain airflow in tubes rather than to prevent alveolar collapse. Consequently, we have evaluated structural, biochemical, and functional parameters of avian surfactant as a model for airway surfactant in the mammalian lung. Surfactant was isolated from duck, chicken, and pig lung lavage fluid by differential centrifugation. Electron microscopy revealed a uniform surfactant layer within the air capillaries of the bird lungs, and there was no tubular myelin in purified avian surfactants. Phosphatidylcholine molecular species of the various surfactants were measured by HPLC. Compared with pig surfactant, both bird surfactants were enriched in dipalmitoylphosphatidylcholine, the principle surface tension-lowering agent in surfactant, and depleted in palmitoylmyristoylphosphatidylcholine, the other disaturated phosphatidylcholine of mammalian surfactant. Surfactant protein (SP)-A was determined by immunoblot analysis, and SP-B and SP-C were determined by gel-filtration HPLC. Neither SP-A nor SP-C was detectable in either bird surfactant, but both preparations of surfactant contained SP-B. Surface tension function was determined using both the pulsating bubble surfactometer (PBS) and capillary surfactometer (CS). Under dynamic cycling conditions, where pig surfactant readily reached minimal surface tension values below 5 mN/m, neither avian surfactant reached values below 15 mN/m within 10 pulsations. However, maximal surface tension of avian surfactant was lower than that of porcine surfactant, and all surfactants were equally efficient in the CS. We conclude that a surfactant composed primarily of dipalmitoylphosphatidylcholine and SP-B is adequate to maintain patency of the air capillaries of the bird lung

Mass spectrometric analysis of surfactant metabolism in human volunteers using deuteriated choline

urfactant reduces surface tension at pulmonary air–liquid interfaces. Although its major component is dipalmitoyl–phosphatidylcholine (PC16:0/16:0), other PC species, principally palmitoylmyristoyl–PC, palmitoylpalmitoleoyl–PC, and palmitoyloleoyl–PC, are integral components of surfactant. The composition and metabolism of PC species depend on pulmonary development, respiratory rate, and pathologic alterations, which have largely been investigated in animals using radiolabeled precursors. Recent advances in mass spectrometry and availability of precursors carrying stable isotopes make metabolic experiments in human subjects ethically feasible. We introduce a technique to quantify surfactant PC synthesis in vivo using deuteriated choline coupled with electrospray ionization tandem mass spectrometry. Endogenous PC from induced sputa of healthy volunteers comprised 54.0 ± 1.5% PC16:0/16:0, 9.7 ± 0.7% palmitoylmyristoyl–PC, 10.0 ± 1.0% palmitoylpalmitoleoyl–PC, and 13.1 ± 0.3% palmitoyloleoyl–PC. Infusion of deuteriated choline chloride (3.6 mg/kg body weight) over 3 hours resulted in linear incorporation into PC over 30 hours. After a plateau of 0.61 ± 0.04% labeled PC between 30 and 48 hours, incorporation decreased to 0.30 ± 0.02% within 7 days. Compared with native PC, fractional label was initially lower for PC16:0/16:0 (31.9 ± 8.3%) but was higher for palmitoyloleoyl–PC (21.0 ± 1.2%), and equilibrium was achieved after only 48 hours. We conclude that infusion of deuteriated choline and electrospray ionization tandem mass spectrometry is useful to investigate surfactant metabolism in humans in vivo

Molecular species compositions of lung and pancreas phospholipids in the cftr(tm1HGU/tm1HGU) cystic fibrosis mouse

Fatty acid analysis of phospholipid compositions of lung and pancreas cells from a cystic fibrosis transmembrane regulator (CFTR) negative mouse (cftr-/-)suggested that a decreased concentration of docosahexaenoate (22:6n-3) and increased arachidonate (20:4n-6) may be related to the disease process in cystic fibrosis (CF). Consequently, we have determined compositions of the major phospholipids of lung, pancreas, liver, and plasma from a different mouse model of CF, the cftrtm1HGU/tm1HGU mouse, compared with ZTM:MF-1 control mice. Electrospray ionization mass spectrometry permitted the quantification of all of the individual molecular species of phosphatidylcholine (PtdCho), phosphatidylethanolamine (PtdEtn), phosphatidylglycerol (PtdGly), phosphatidylserine (PtdSer), and phosphatidylinositol (PtdIns). There was no deficiency of 22:6n-3 in any phospholipid class from lung, pancreas, or liver from mice with the cftrtm1HGU/tm1HGU. Instead, the concentration of 20:4n-6 was significantly decreased in plasma PtdCho species and in pancreas and lung species of PtdEtn, PtdSer, and PtdIns. These results demonstrate the variability of membrane phospholipid compositions in different mouse models of CF and suggest that in cftrtm1HGU/tm1HGU mice, the apparent deficiency was of 20:4n-6- rather than of 22:6n-3–containing phospholipid species. They highlight a need for detailed phospholipid molecular species analysis of cells expressing mutant CFTR from children with CF before the therapeutic effects of administering high doses of 22:6n-3–containing oils to children with CF can be fully evaluated