title: Respiratory adaptation and surfactant composition of unanesthetized male and female lambs differ for up to 8 h after preterm birth.
abstract: BACKGROUND
  Male preterm infants are more likely to experience respiratory distress syndrome than females. Our objectives were to determine if sex-related differences in physiological adaptation after preterm birth increase with time after birth and if the use of continuous positive airway pressure (CPAP) reduces these differences.
  
  
  METHODS
  Unanesthetized lambs (9F, 8M) were delivered at 0.90 of term. Blood gases, metabolites, and cardiovascular and respiratory parameters were monitored in spontaneously breathing lambs for 8 h. Supplemental oxygen was administered via a face mask at 4 cmH2O CPAP. At 8 h, lung compliance was determined, and bronchoalveolar lavage fluid (BALF) was analyzed for total protein and surfactant phospholipids. Surfactant protein (SP) gene expression and protein expression of SP-A and pro-SP-C were determined in lung tissue.
  
  
  RESULTS
  For 8 h after delivery, males had significantly lower arterial pH and higher Paco2, and a greater percentage of males were dependent on supplemental oxygen than females. Inspiratory effort was greater and lung compliance was lower in male lambs. Total protein concentration in BALF, SP gene expression, and SP-A protein levels were not different between sexes; pro-SP-C was 24% lower in males.
  
  
  CONCLUSIONS
  The use of CPAP did not eliminate the male disadvantage, which continues for up to 8 h after preterm birth.
authors.affiliation: Development and Stem Cells Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Australia.
authors.forename: Robert
authors.identifier: http://orcid.org/0000-0001-7676-4646
authors.initials: R
authors.lastname: De Matteo
authors.affiliation: Development and Stem Cells Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Australia.
authors.forename: Noreen
authors.initials: N
authors.lastname: Ishak
authors.affiliation: Development and Stem Cells Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Australia.|Department of Pediatrics, Tohoku University School of Medicine, Aobaku, Sendai, Japan.
authors.forename: Takushi
authors.initials: T
authors.lastname: Hanita
authors.affiliation: Development and Stem Cells Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Australia.
authors.forename: Richard
authors.initials: R
authors.lastname: Harding
authors.affiliation: Development and Stem Cells Program, Monash Biomedicine Discovery Institute and Department of Anatomy and Developmental Biology, Monash University, Melbourne, Australia.
authors.forename: Foula
authors.initials: F
authors.lastname: Sozo
mesh_terms: D000222:Adaptation, Physiological; D000818:Animals; D000831:Animals, Newborn; D001835:Body Weight; D001992:Bronchoalveolar Lavage Fluid / Q000737:chemistry; D002245:Carbon Dioxide / Q000097:blood; D045422:Continuous Positive Airway Pressure; D005260:Female; D005325:Fetal Organ Maturity; D018507:Gene Expression Regulation, Developmental; D006863:Hydrogen-Ion Concentration; D008168:Lung / Q000196:embryology / Q000378:metabolism; D008170:Lung Compliance; D008297:Male; D009929:Organ Size; D010100:Oxygen / Q000008:administration & dosage / Q000097:blood; D010743:Phospholipids / Q000032:analysis; D047928:Premature Birth / Q000378:metabolism / Q000503:physiopathology*; D037662:Pulmonary Surfactant-Associated Protein A / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D037701:Pulmonary Surfactant-Associated Protein B / Q000096:biosynthesis / Q000737:chemistry* / Q000235:genetics; D012127:Respiratory Distress Syndrome, Newborn / Q000097:blood / Q000503:physiopathology*; D012137:Respiratory System / Q000503:physiopathology*; D012727:Sex Characteristics; D012756:Sheep; D014781:Viscera / Q000033:anatomy & histology
chemical_list: D010743:Phospholipids; D037662:Pulmonary Surfactant-Associated Protein A; D037701:Pulmonary Surfactant-Associated Protein B; D002245:Carbon Dioxide; D010100:Oxygen