Intramembranous solute and water fluxes during high intramembranous absorption rates in fetal sheep with and without lung liquid diversion.
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.
Gesteland
Katherine M
KM
Departments of Obstetrics and Gynecology, Oregon Health and Science University, Portland, OR, USA.
Anderson
Debra F
DF
Davis
Lowell E
LE
Robertson
Patricia
P
Faber
J Job
JJ
Brace
Robert A
RA
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
D002712:Chlorides; D012964:Sodium; D002118:Calcium