title: The role of lung inflation and sodium transport in airway liquid clearance during lung aeration in newborn rabbits.
abstract: BACKGROUND
  Recent phase-contrast X-ray imaging studies suggest that inspiration primarily drives lung aeration and airway liquid clearance at birth, which questions the role of adrenaline-induced activation of epithelial sodium channels (ENaCs). We hypothesized that pressures generated by inspiration have a greater role in airway liquid clearance than do ENaCs after birth.
  
  
  METHODS
  Rabbit pups (30 d of gestation) were delivered and sedated, and 0.1 ml of saline (S) or amiloride (Am; an ENaC inhibitor) was instilled into the lungs before mechanical ventilation. Two other groups (30 d of gestation) were treated similarly but were also given adrenaline (S/Ad and Am/Ad) before mechanical ventilation.
  
  
  RESULTS
  Amiloride and adrenaline did not affect functional residual capacity (FRC) recruitment (P > 0.05). Amiloride increased the rate of FRC loss between inflations (Am: -5.2 ± 0.6 ml/kg/s), whereas adrenaline reduced the rate of FRC loss (S/Ad: -1.9 ± 0.3 ml/kg/s) as compared with saline-treated controls (S: -3.5 ± -0.6 ml/kg/s; P < 0.05).
  
  
  CONCLUSIONS
  These data indicate that inspiration is a major determinant of airway liquid clearance and FRC development during positive pressure ventilation. Although ENaC inhibition and adrenaline administration had no detectable effect on FRC development, ENaC may help to prevent liquid from re-entering the airways during expiration.
authors.affiliation: Ritchie Centre, Monash Institute of Medical Research, Monash University, Clayton, Australia. melissa.siew@monash.edu
authors.forename: Melissa L
authors.initials: ML
authors.lastname: Siew
authors.forename: Megan J
authors.initials: MJ
authors.lastname: Wallace
authors.forename: Beth J
authors.initials: BJ
authors.lastname: Allison
authors.forename: Marcus J
authors.initials: MJ
authors.lastname: Kitchen
authors.forename: Arjan B
authors.initials: AB
authors.lastname: te Pas
authors.forename: M Sirajul
authors.initials: MS
authors.lastname: Islam
authors.forename: Robert A
authors.initials: RA
authors.lastname: Lewis
authors.forename: Andreas
authors.initials: A
authors.lastname: Fouras
authors.forename: Naoto
authors.initials: N
authors.lastname: Yagi
authors.forename: Kentaro
authors.initials: K
authors.lastname: Uesugi
authors.forename: Stuart B
authors.initials: SB
authors.lastname: Hooper
mesh_terms: D000584:Amiloride / Q000008:administration & dosage; D000818:Animals; D000831:Animals, Newborn; D004837:Epinephrine / Q000008:administration & dosage; D062686:Epithelial Sodium Channel Blockers / Q000008:administration & dosage; D053503:Epithelial Sodium Channels / Q000187:drug effects / Q000378:metabolism*; D005652:Functional Residual Capacity; D005865:Gestational Age; D006874:Hydrostatic Pressure; D001239:Inhalation; D008168:Lung / Q000000981:diagnostic imaging / Q000187:drug effects / Q000378:metabolism*; D008176:Lung Volume Measurements; D009079:Mucociliary Clearance; D010991:Plethysmography; D011817:Rabbits; D011859:Radiography; D012121:Respiration, Artificial; D020545:Respiratory Mucosa / Q000187:drug effects / Q000378:metabolism*; D012964:Sodium / Q000378:metabolism*; D012965:Sodium Chloride / Q000008:administration & dosage; D013997:Time Factors
chemical_list: D062686:Epithelial Sodium Channel Blockers; D053503:Epithelial Sodium Channels; D012965:Sodium Chloride; D000584:Amiloride; D012964:Sodium; D004837:Epinephrine