title: Intramembranous solute and water fluxes during high intramembranous absorption rates in fetal sheep with and without lung liquid diversion.
abstract: OBJECTIVE
  To examine mechanisms that mediate increased intramembranous solute and water absorption.
  
  
  METHODS
  Intramembranous solute and water fluxes were measured in fetal sheep under basal conditions and after intraamniotic infusion of lactated Ringer's solution of 4 L/d for 3 days with and without lung liquid diversion.
  
  
  RESULTS
  Intramembranous sodium, potassium, chloride, calcium, glucose, and lactate fluxes increased 2.5- to 7.9-fold, were linearly related to volume fluxes (r = 0.83-0.99), and were unaffected by lung liquid. All clearance rates, except that of lactate, increased to equal the intramembranous volume absorption rate during infusion.
  
  
  CONCLUSIONS
  Under basal conditions, passive diffusion makes a minor and bulk flow a major contribution to intramembranous solute absorption. During high absorption rates, the increase in solute absorption above basal levels appears to be due entirely to bulk flow and is unaffected by lung liquid. The increased bulk flow is consistent with vesicular transcytosis.
authors.affiliation: Departments of Obstetrics and Gynecology, Oregon Health and Science University, Portland, OR, USA.
authors.forename: Katherine M
authors.initials: KM
authors.lastname: Gesteland
authors.forename: Debra F
authors.initials: DF
authors.lastname: Anderson
authors.forename: Lowell E
authors.initials: LE
authors.lastname: Davis
authors.forename: Patricia
authors.initials: P
authors.lastname: Robertson
authors.forename: J Job
authors.initials: JJ
authors.lastname: Faber
authors.forename: Robert A
authors.initials: RA
authors.lastname: Brace
mesh_terms: D000042:Absorption; D000653:Amniotic Fluid / Q000737:chemistry / Q000378:metabolism / Q000502:physiology*; D000818:Animals; D002118:Calcium / Q000032:analysis; D002712:Chlorides / Q000032:analysis; D004058:Diffusion; D005321:Extraembryonic Membranes / Q000502:physiology*; D005260:Female; D005333:Fetus / Q000378:metabolism*; D006706:Homeostasis / Q000502:physiology*; D023421:Models, Animal; D015999:Multivariate Analysis; D009995:Osmosis; D011247:Pregnancy; D012756:Sheep; D012964:Sodium / Q000032:analysis; D014132:Trachea / Q000196:embryology
chemical_list: D002712:Chlorides; D012964:Sodium; D002118:Calcium