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Surfactant Synthesis and Kinetics in Infants with Congenital Diaphragmatic Hernia

Department of Pediatrics, Division of Pediatric Surgery, and Institute of Internal Medicine, University of Padova, Padova, Italy; Department of Pediatrics, Erasmus University, Rotterdam, The Netherlands; and Institute of Child Health and Great Ormond Street Hospital, London, United Kingdom

Correspondence and requests for reprints should be addressed to Virgilio P. Carnielli, M.D., Ph.D., Senior Lecturer, Pediatric Nutrition, Institute of Child Health, Great Ormond Street Hospital, 30 Guilford Street, MRC CNRC Room W.4.03, London WC1N 1EH, UK. E-mail: v.carnielli{at}ich.ucl.ac.uk

	ABSTRACT

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In animal models of congenital diaphragmatic hernia (CDH), surfactant deficiency contributes to the pathophysiology of the disease; however, information on CDH in humans is limited. We compared surfactant disaturated phosphatidylcholine (DSPC) synthesis and metabolism, by stable isotope technology, in newborn infants with CDH and in control subjects. DSPC amount, total proteins, and surfactant protein–A (SP-A) from tracheal aspirates were also measured. DSPC and SP-A were significantly lower in 14 infants with CDH than in the eight control subjects. Mean DSPC was 2.3 ± 1.3 mg/ml of epithelial lining fluid (ELF) in infants with CDH and 4.6 ± 1.5 mg/ml of ELF in control subjects (p = 0.001). Mean SP-A in infants with CDH and in control subjects was 16.2 ± 9.3 and 61.2 ± 30.6 µg/ml of ELF, respectively (p = 0.03). DSPC kinetics was measured in 12 of 14 infants with CDH and in 5 of 8 control subjects. Secretion time was 8.3 ± 5.5 and 8.5 ± 2.5 hours and peak time 51.9 ± 15.2 and 51 ± 13 hours in infants with CDH and in control subjects, respectively. Fractional synthesis rate was not different for infants with CDH and control subjects (p = 0.4). In conclusion, surfactant DSPC synthesis and kinetics were not significantly deranged in infants with CDH compared with control subjects. Other factors, such as lower surface area or increased DSPC catabolism, may contribute to surfactant pool alteration in CDH.

Key Words: surfactant • congenital diaphragmatic hernia • stable isotopes

	INTRODUCTION

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Congenital diaphragmatic hernia (CDH) remains an unsolved problem, with high morbidity and mortality despite recent advances in respiratory support. Pulmonary hypoplasia and persistent pulmonary hypertension are the landmarks of the disease, but both morphologic and biochemical lung immaturity are also present. Evidence of biochemical lung immaturity comes mainly from two experimental models: surgical CDH in fetal lambs (1), and chemical CDH in rats induced by 2,4-dichlorophenyl-p-nitrophenyl ether (TOK or nitrofen) during pregnancy (2). In these animal models, lung biochemical immaturity was assessed by morphometric analysis, glycogen concentrations, and disaturated phosphatidylcholine (DSPC) lung content (3) as well as lecithin/sphingomyelin ratio, phosphatidylglycerol concentration (4, 5), and surfactant protein–A (SP-A) concentration in the amniotic fluid (6). In bronchoalveolar lavage fluid of lambs with CDH, the total amount of phospholipids and the percentage of phosphatidylcholine were significantly lower compared with control animals (7), whereas lecithin/sphingomyelin ratio and phosphatidylglycerol concentrations in the amniotic fluids of the same animals were normal. Furthermore, decreased DSPC concentrations have been observed in the lungs of rat pups with CDH (4). A more recent study suggests that differences in surfactant specific protein composition and content are related to lung immaturity, and that they disappeared by the end of gestation in rat pups with CDH (8).

In humans with CDH, biochemical immaturity has been assessed in nonsurvivor CDH lungs (9), in amniotic fluid, and, more recently, in bronchoalveolar lavage (10). In lung tissue of infants with CDH, the DSPC concentration was lower in most of the affected lungs compared with age-matched control subjects (9). In the amniotic fluid of infants with CDH, decreased values of lecithin/sphingomyelin ratios, DSPC concentrations, and SP-A concentrations have been reported (11, 12), whereas other researchers found normal lecithin/sphingomyelin ratios and phosphatidyglycerol (7) in the amniotic fluid of the same animal model. In bronchoalveolar lavage of infants with CDH, a recent study by Ijsselstijn and coworkers reported concentrations of phosphatidylcholine, phosphatidylglycerol, and lecithin/sphingomyelin ratios similar to those of age-matched control infants (10), suggesting that a primary surfactant deficiency is unlikely in infants with CDH. Moreover, phosphatidylcholine concentrations in bronchoalveolar lavage seemed not to decrease over time in the same group of infants, although data showed a wide range of variation. In the study by Ijsselstijn and coworkers, however, the control group had severe respiratory failure, which could also have led to secondary surfactant deficiency (10).

Recently, we developed a method to measure surfactant synthesis and turnover in vivo in human infants by means of stable isotopes (13). We applied this new technique to study whether the endogenous DSPC surfactant synthesis is impaired in newborn infants with CDH compared with newborn infants with normal lungs.

	METHODS

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Patients and Study Design
Surfactant kinetics, tracheal aspirate (TA) DSPC, and SP-A were studied in 14 infants with CDH and in 8 newborns with normal lungs. All patients were admitted to the Neonatal Intensive Care Unit, Padova, Italy. Inclusion criteria were the following: (1) respiratory failure due to CDH or upper airway obstruction, or abdominal wall defects and normal lungs; (2) arterial and venous lines for clinical monitoring; (3) written informed consent from parents; (4) no exogenous surfactant administered; and (5) stable cardiorespiratory conditions for at least 18 hours after birth.

Blood pressure and pre- and postductal arterial saturations were monitored continuously, and blood gases were checked at least every 8 hours in infants with CDH and once a day in control subjects.

The study was approved by the Ethics Committee of the Azienda Ospedaliera di Padova, and written informed consent was obtained from both parents.

Surfactant Kinetics
Infants received a 24-hour constant intravenous infusion of [U-¹³C] palmitic acid (PA) (Martek, Columbia, MD) bound to albumin (13, 14) when on a lipid-free intravenous infusion. Time zero was defined by the start of the infusion, which started in infants with CDH within 3 days and in control subjects within 5 days of birth. TA and blood were collected as reported (13). DSPC from TA was purified by thin layer chromatography after treatment with osmium tetroxide (15), and free fatty acids were extracted from blood and separated by thin layer chromatography (14, 16). Isotopic enrichments were measured by mass spectrometry (15).

Enrichments were expressed as atom percent excess (14). No amniotic fluid or TA was collected at birth.

Protein Assay
Protein assay in TA was performed using a Cobas Mira autoanalyzer (Roche, Milan, Italy) with Pyrogallol (Analitica Triveneta s.r.l., Padova, Italy), using bovine albumin as standard at 100 mg/ml (17). The coefficient of variation was 3.8%.

Urea Assay
Urea assay in TA was performed using a Cobas Mira autoanalyzer (Roche), with Urea MPR2 (Boehringer Mannheim) (18). A standard solution of 421 µm/L of urea in saline was used for the analysis. The coefficient of variation was 6.5%. Plasma urea was measured by the standard immunoenzymatic method. Dilution of epithelial lining fluid (ELF) was calculated as ELF volume (per milliliter of return fluid), [urea]_TA/[urea]_PLASMA (18, 19).

SP-A
SP-A has been detected by enzyme linked immunosorbent assay, using a polyclonal antibody anti-human SP-A (20).

Surfactant Kinetic Parameters
A steady state could be assumed because (1) surfactants in the Type II cells and on the alveolar surface were regarded as one pool, as surfactant recycling is much faster than de novo synthesis and clearance (20–22); and (2) DSPC pool size in animal models increases during the perinatal period and remains stable in the first week of age (23). The following surfactant kinetic parameters could be calculated in infants with CDH and control subjects: fractional synthesis rate (FSR), secretion time (ST), peak time (PT), and half-life (HL) (13, 25).

Data are presented as mean ± SD. Mean DSPC and SP-A values were calculated by obtaining the average of all time points for each patient and then the means for the patients in each group. Comparisons were done by a nonparametric t test. The level of significance was p < 0.05. Correlations were calculated within the CDH group with Pearson correlation.

	RESULTS

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We studied 14 infants with CDH and 8 control subjects. Clinical characteristics of the patients with CDH are shown in Table 1. Twelve of 14 infants with CDH and 5 of 8 control subjects received isotope infusions long enough to obtain data on surfactant kinetics. The two groups were matched for weight (p = 0.17), gestational age (p = 0.28), and postnatal age, although the last one was close to statistical significance (p = 0.06). Five infants with CDH died before hospital discharge, two of them 16 and 24 hours after the start of the study. No DSPC kinetic data were obtained from these two infants. Eleven infants with CDH were ventilated on high frequency oscillatory ventilation (HFOV) during the study, and three infants with CDH and all control subjects were on conventional ventilation. None of the infants received extra corporeal membrane oxygenation (ECMO). Three of the eight control subjects did not receive any isotope infusion because parent consent was not obtained. No systemic hypotension or pre- or postductal desaturation differences were recorded during the study period in any patients.

View larger version (24K): [in this window] [in a new window]   Figure 1. In Panels A and C we plot all TA protein content measured in infants with CDH and control infants, respectively, during the study period. Protein amounts are higher in infants with CDH, especially during the first 5 days of the study (120 hours), compared with control subjects. Panels B and D depict TA DSPC plots in infants with CDH and control subjects over time. Mean DSPC amount was lower in infants with CDH compared with control infants throughout the study period.

View larger version (14K): [in this window] [in a new window]   Figure 2. Amount of TA SP-A per milliliter ELF in infants with CDH (black squares) and in control subjects (open dots). TA SP-A was significantly lower in the CDH group compared with that in control subjects, and it decreased over time only in infants with CDH.

A significant incorporation of the intravenously infused labeled-PA was measurable in the surfactant DSPC from all patients. Kinetic data calculated for each individual patient are shown in Figure 3. Surfactant DSPC HL could be reliably calculated for 4 of 5 control subjects and for 10 of 12 infants with CDH. Patients with missing values were extubated shortly after 60 hours from the start of the study.

View larger version (14K): [in this window] [in a new window]   Figure 3. Surfactant DSPC FSR (FSR), ST (ST), PT (Peak), and HL (Half Life) after a 24-hour intravenous infusion of [U-13C] PA in 12 newborn infants with CDH (black bars) and in five age-matched control subjects (open bars). No statistical significance was found for FSR (p = 0.3), ST (p = 0.9), PT (p = 0.9), or HL (p = 0.2).

	DISCUSSION

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This study measured for the first time surfactant DSPC kinetics in newborn infants with CDH. Data on DSPC, total protein, and SP-A content in TA of newborns with CDH and with normal lungs, and correlation with kinetic data are also reported.

Infants with CDH exhibited significantly lower DSPC and SP-A in TA. These values decreased further during the study period compared with age-matched infants with no lung disease. These findings are suggestive of a surfactant deficiency in our patients with CDH, which could reflect a smaller alveolar surface area in the affected lungs or be due to decreased synthesis or increased catabolism of alveolar surfactant (24). Although it is very likely that these differences were due to the lung condition (infants with CDH versus control subjects), in principle it cannot be excluded that differences in ventilator support and inspired oxygen may have contributed to the differences found at study time 0, which on average occurred at 31 hours of life. Our control group had no apparent lung disease and did require minimal amount of supplemental oxygen while on mechanical ventilation, and thus it represented the best possible control group of mechanically ventilated newborn infants (25). As shown by others (26), we also found that the protein content in TA was higher in infants with CDH during the first few days of life compared with that in control subjects, although the difference in our study was not statistically significant (1). Higher protein content in TA could result from lung immaturity, ventilation, and oxygen-induced lung injury. Although the protein content found in TA from infants with CDH was not markedly elevated, it is possible that proteins contributed to a reduction of surfactant activity (1).

SP-A amount in TA of infants with CDH was approximately 25% of the control values during the study period. Low amounts of SP-A have been reported in amniotic fluid of human pregnancies (12), and low SP-A mRNA amounts have been shown in lungs of nitrofen-induced CDH rat model at different gestational ages (6), and in term lambs with surgically induced CDH (27). The mechanisms responsible for a decrease in expression of SP-A in CDH Type II cells may be related, at least in part, to the chronic compression of the lungs, which may limit the growth-promoting stimulus of lung stretch and fetal breathing movements (28). After birth, the low alveolar surface can contribute to the reduced DSPC and SP-A pool size.

The novel information of the study is that the endogenous surfactant synthesis as expressed as DSPC FSR from PA was not statistically different between infants with CDH and control subjects (22% per day in CDH versus 17% per day in control subjects, p = 0.16). We also found that DSPC FSR positively correlated with TA amount of DSPC over the study period (p = 0.008, R = 0.7). The meaning of the DSPC FSR as compared with the absolute synthesis rate has been discussed at length elsewhere (29). It is notable that a decreased DSPC pool size may result in a higher than expected DSPC FSR. In this study, we have no information on the DSPC pool size in infants with CDH. We assumed a steady state condition, which implies that the amount of DSPC removed equaled the DSPC replacement on the alveolar surface. Given that the mean DSPC FSR in the CDH group was greater than in control subjects by about 30%, a similar ASR could be expected if lung DSPC pool size in the CDH group were to be reduced down to 30% less than in control subjects. On the other hand, if the mean DSPC pool size were reduced by more than 30% in the CDH group, we could have hypothesized a reduced DSPC synthesis and/or secretion based on ¹³C-PA enrichments in DSPC TA. In animal studies, steady state can be proved by direct measurement of DSPC pool size at different time points during the study period. This is not feasible in vivo in human infants. We therefore provided the following three points as indirect evidence of steady state: (1) we plotted ELF DSPC for each infant over the study period, and all the obtained slopes were not different from zero (data not shown); (2) all subjects were studied beyond the period of the rapid changes of surfactant pools that occur in the first 24 hours of life (23); (3) all study infants were on a constant degree of ventilatory support, indicating a stable clinical and respiratory condition. Despite the previous three considerations, if a steady state were not present in our sick, but clinically stable, infants with CDH, even a pool size change of 10% per day (which would lead to a total DSPC pool loss in about 15 days) would result in an overestimation of DSPC FSR value of about 15%. This would not change the main result of our study.

A 22% DSPC FSR in the CDH group represents the mean of widely scattered values. We did not find any correlation with the degree of lung hypoplasia, although the small number of infants did not allow us to draw any conclusion. It is also to be kept in mind that CDH lungs may be under "maximal stimulation" for surfactant synthesis, whereas control lungs were not, and therefore, an impaired DSPC synthesis or secretion cannot be excluded with the present study design. We are in the process of studying whether or not neonates with congenitally normal lungs but with conditions such as meconium aspiration syndrome (MAS) of neonatal pneumonia and requiring significant ventilator support and high fractions of inspired oxygen are able to mount a much greater DSPC synthesis than infants with CDH on comparable ventilator settings. It is notable, however, that DSPC ST, PT, and HL are similar in infants with CDH and in control newborns, in support of a comparable rate of synthesis and secretion in the two groups.

Other factors that affect incorporation of PA in surfactant DSPC have to be considered, such as the effect of pulmonary hypertension and ventilator modes.

Severe pulmonary hypertension with right-to-left shunt through ductus Botalli may be associated with CDH. Under these circumstances, less blood flow passes through the lungs, and therefore, fewer surfactant metabolic precursors may reach the Type II cells. In all our infants, we could not show any clinical sign of pulmonary hypertension during the isotope infusion. Therefore, we assumed that the label was adequately and equally provided to both study groups.

Mechanical ventilation per se does affect DSPC biosynthesis. It has been reported that incorporation of injected radioactively labeled PA into DSPC alveolar fraction increased significantly in a group of ventilated rabbits compared with spontaneously breathing animals (30, 31). In the present study, all infants were on mechanical ventilation, and 79% of infants with CDH were on HFOV. We have recently studied surfactant phosphatidylcholine synthesis in 19 preterm infants, randomized either to HFOV or to conventional ventilation, receiving a continuous infusion of U-¹³C glucose. We could not demonstrate any difference on phosphatidylcholine FSR, or any difference on the other phosphatidylcholine kinetic parameters in the two randomized groups. Whether this might also be applied to the CDH hypoplastic lungs is still to be determined.

It is also important to note that the TA sampling site in our study is just below the endotracheal tube and above the carina, meaning that we studied the contribution of both lungs to surfactant components and kinetics. Therefore, we were not able to ascertain if in infants with CDH the most affected lung had different DSPC kinetics compared with the healthier lung.

Few studies are available on surfactant synthesis in CDH animal models, and they show contradictory results. In fetal lamb with surgically induced CDH, the rate of synthesis by isolated Type II cells obtained from CDH lambs was decreased, although the difference did not reach statistical significance (1). In cultures of Type II cells from rat fetuses with severe CDH, Zimmermann and colleagues found a reduced activity of the phosphocholine cytidiltransferase, which regulates the de novo synthesis of phosphatidylcholine (32). Stone and Manson studied the effect of nitrofen on the lung development of normal rat fetuses. They showed that nitrofen did not affect the DSPC synthesis, as the total phospholipid content, choline incorporation, and phosphocholine cytidiltransferase activity were similar to those in control animals (33). Moreover, when each lung in a lung model of CDH was examined, Wilcox and coworkers found that the biosynthetic pathway of Type II cells isolated from CDH lungs was lower, not only compared with control subjects but also compared with the contralateral CDH lungs (26). The lack of biochemical surfactant differences between the two CDH lungs reported in this study has been explained using radiolabeled exogenous surfactant injected in the contralateral lung, as an in utero mixing of lung fluid (26).

In conclusion, this study showed moderately but significantly reduced amounts of DSPC in CDH and also a marked reduction of SP-A from TA of CDH infants throughout the study period. Nonetheless, by using a novel method we found comparable rates of endogenous DSPC synthesis in infants with CDH and in control neonates. We speculate that surfactant alteration in CDH may be more related to enhanced catabolism than impaired synthesis or that other factors such as surfactant proteins or secretion impairments may lead to reduced levels of alveolar surfactant. Further studies are in progress to clarify if surfactant synthesis can be enhanced in patients with CDH by prenatal steroids (34) and to ascertain the cause of the reduced amount of surfactant from TA.

	Acknowledgments

 
The authors are extremely grateful to the nurses of the Neonatal Intensive Care. Without their precious contribution this study would not have been possible. The authors would like to dedicate this study to Marco B. and to his parents, who were extremely supportive to our research efforts. Marco had CDH, he participated in the study, and he is now growing healthy and full of life.

The study has received grants from the Department of Medical Research, Veneto Region, Italy and Consorzio Malattie Rare (C.o.M.a.R, Rome, Italy).

Received in original form August 7, 2001; accepted in final form March 22, 2002

	REFERENCES

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1. Glick PL, Stannard VA, Leach CL, Rossman J, Hosada Y, Morin FC, Cooney DR, Allen JE, Holm B. Pathophysiology of congenital diaphragmatic hernia II: the fetal lamb CDH model is surfactant deficient. J Pediatr Surg 1992;27:382–387.[CrossRef][Medline]
2. Iritani I. Experimental study on embryogenesis of congenital diaphragmatic hernia. Anat Embryol 1984;169:133–139.[CrossRef][Medline]
3. Suen HC, Bloch KD, Donahoe PK. Antenatal glucocorticoid corrects pulmonary immaturity in experimentally induced congenital diaphragmatic hernia in rats. Pediatr Res 1994;35:523–529.[Medline]
4. Suen HC, Catlin EA, Ryan DP, Wain JC, Donahoe PK. Biochemical immaturity of lung in congenital diaphragmatic hernia. J Pediatr Surg 1993;28:471–475.[CrossRef][Medline]
5. Wilcox DT, Glick PL, Karamanoukian HL, Azizkhan RG, Holm BA. Pathophysiology of congenital diaphragmatic hernia: XII. Amniotic fluid lecithin/sphingomyelin ratio and phosphatidylglycerol concentrations do not predict surfactant status in congenital diaphragmatic hernia. J Pediatr Surg 1995;30:410–412.[CrossRef][Medline]
6. Mysore MR, Margraf LR, Jaramillo MA, Breed DR, Chau VL, Arevalo M, Moya FR. Surfactant protein A is decreased in a rat model of congenital diaphragmatic hernia. Am J Respir Crit Care Med 1998;157:654–657.[Abstract/Free Full Text]
7. Sullivan KM, Hawgood S, Flake AW, Harrison MR, Adzick NS. Amniotic fluid phospholipid analysis in the fetus with congenital diaphragmatic hernia. J Pediatr Surg 1994;29:1020–1023.[CrossRef][Medline]
8. Blommaart PJE, van Tuyl WG, Keijzer M, Lamer WH, Tibboel D. Clearance of treatment doses of surfactant. Am J Respir Crit Care Med 1997;155:A949.
9. Nakamura Y, Yamamoto I, Fukuda S, Hashimoto T. Pulmonary acinar development in diaphragmatic hernia. Arch Pathol Lab Med 1991;115:372–376.[Medline]
10. Ijsselstijn H, Zimmermann LJ, Bunt JE, de Jongste JC, Tibboel D. Prospective evaluation of surfactant composition in bronchoalveolar lavage fluid of infants with congenital diaphragmatic hernia and of age-matched controls. Crit Care Med 1998;26:573–580.[CrossRef][Medline]
11. Berk C, Grundy M. High risk lecithin/sphingomyelin ratios associated with neonatal diaphragmatic hernia: case reports. Br J Obstet Gynaecol 1982;89:250–251.[Medline]
12. Moya FR, Thomas VL, Romaguera J, Mysore MR, Maberry M, Bernard A, Freund M. Fetal lung maturation in congenital diaphragmatic hernia. Am J Obstet Gynecol 1995;173:1401–1405.[CrossRef][Medline]
13. Cogo PE, Carnielli VP, Bunt JEH, Badon T, Giordano G, Zacchello F, Sauer PJJ, Zimmermann LJI. Endogenous surfactant metabolism in critically ill infants measured with stable isotopes labeled fatty acids. Pediatr Res 1999;45:242–246.[Medline]
14. Cogo PE, Giordano G, Badon T, Orzali A, Zimmermann LJI, Zacchello F, Sauer PJJ, Carnielli VP. Simultaneous measurement of the rate of appearance of palmitic and linoleic acid in critically ill infants. Pediatr Res 1997;41:178–182.[Medline]
15. Torresin M, Zimmermann LJI, Cogo PE, Cavicchioli P, Badon T, Giordano G, Zacchello F, Sauer PJJ, Carnielli VP. Exogenous surfactant kinetics in infant respiratory distress syndrome: a novel method with stable isotopes. Am J Respir Crit Care Med 2000;161:1584–1589.[Abstract/Free Full Text]
16. Carnielli VP, Pederzini F, Vittorangeli R, Luijendijk IH, Boomaars WE, Pedrotti D, Sauer PJ. Plasma and red blood cell fatty acid of very low birth weight infants fed exclusively with expressed preterm human milk. Pediatr Res 1996;39:671–679.[Medline]
17. Watanabe N, Kamei S, Ohkubo A, Yamanaka M, Ohsawa S, Makino K, Tokuda K. Urinary protein as measured with a pyrogallol red-molybdate complex, manually and in a Hitachi 726 automated analyzer. Clin Chem 1986;32:1551–1554.[Abstract/Free Full Text]
18. Rennard SI, Basset G, Lecossier D, O'Donnell KM, Pinkston P, Martin PG, Crystal RG. Estimation of volume of epithelial lining fluid recovered by lavage using urea as marker of dilution. J Appl Physiol 1986;60:532–538.[Abstract/Free Full Text]
19. Dargaville PA, South M, Vervaart P, McDougall PN. Validity of markers of dilution in small volume lung lavage. Am J Respir Crit Care Med 1999;160:778–784.[Abstract/Free Full Text]
20. Baritussio A, Alberti A, Quaglino D, Pettenazzo A, Dalzoppo D, Sartori L, Pasquali Ronchetti I. SP-A, SP-B, and SP-C in surfactant subtypes around birth: reexamination of alveolar life cycle of surfactant. Am J Physiol 1994;266:L436–L447.[Abstract/Free Full Text]
21. Ikegami M, Jobe AH, Yamada T, Priestly A, Ruffini L, Rider E. Surfactant metabolism in surfactant-treated preterm ventilated lambs. J Appl Physiol 1989;67:429–437.[Abstract/Free Full Text]
22. Jacobs H, Jobe A, Ikegami M, Jones S. Surfactant phosphatidylcholine source, fluxes, and turnover times in 3-day-old, 10-day-old, and adult rabbits. J Biol Chem 1982;257:1805–1810.[Abstract/Free Full Text]
23. Bruni R, Baritussio A, Quaglino D, Gabelli C, Benevento M, Ronchetti IP. Postnatal transformations of alveolar surfactant in the rabbit: changes in pool size, pool morphology and isoforms of the 32–38 kD apolipoprotein. Biochim Biophys Acta 1988;958:255–267.[Medline]
24. Godinez MH, Godinez RI. Inspired oxygen concentration alters the phospholipid and protein content in the bronchoalveolar lavage-accessible space. Crit Care Med 1996;24:862–869.[CrossRef][Medline]
25. Mc Cabe AJ, Irish MS, Holm BA, Glick PL. Inspired oxygen concentration alters the phospholipids and protein content in the bronchoalveolar lavage-accessible space. Crit Care Med 1999;27:1219–1222.[Medline]
26. Wilcox DT, Glick PL, Karamanoukian HL, Holm BA. Contributions by individual lungs to the surfactant status in congenital diaphragmatic hernia. Pediatr Res 1997;41:686–691.[Medline]
27. Wilcox DT, Irish MS, Holm BA, Glick PL. Pulmonary parenchymal abnormalities in congenital diaphragmatic hernia. Clin Perinatol 1996;23:771–779.[Medline]
28. Liu M, Xu J, Tanwswell K, Post M. Stretch-induced growth-promoting activities stimulate fetal rat lung epithelial cell proliferation. Exp Lung Res 1993;19:505–517.[Medline]
29. Cavicchioli P, Zimmermann LJ, Cogo PE, Badon T, Giordano G, Torresin M, Zacchello F, Carnielli VP. Endogenous surfactant turnover in preterm infants with respiratory distress syndrome studied with stable isotope lipids. Am J Respir Crit Care Med 2001;163:55–60.[Abstract/Free Full Text]
30. Ennema JJ, Reijngoud DJ, Egberts J, Mook PH, Wildevuur CR. High-frequency oscillation affects surfactant phospholipid metabolism in rabbits. Respir Physiol 1984;58:29–39.[CrossRef][Medline]
31. Ennema JJ, Reijngoud DJ, Wildevuur CR, Egberts J. Effects of artificial ventilation on surfactant phospholipid metabolism in rabbits. Respir Physiol 1984;58:15–28.[CrossRef][Medline]
32. Zimmermann LJ, Ijsselstijn H, Scheffers EC, Sayer PJ, Batemburg JJ, Tibboel D. Decreased activity of phosphocholine cytidyltransferase in type II pneumocytes from rats with congenital diaphragmatic hernia (CDH). Pediatr Res 1994;35:359A.
33. Stone LC, Manson JM. Effects of the herbicide 2,4-dichlorophenyl-pnitrophenyl ether (nitrofen) on fetal lung development in rats. Toxicology 1981;20:195–208.[CrossRef][Medline]
34. Bunt JEH, Carnielli VP, Wattimena JLD, Sauer PJJ, Zimmermann LJI. The effect of prenatal corticosteroids on endogenous surfactant synthesis in premature infants, measured with stable isotopes. Am J Respir Crit Care Med 2000;162:844–849.[Abstract/Free Full Text]

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