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Permeability of placenta to inulin
K L Thornburg1, K J Burry, A K Adams
1Department of Physiology, School of Medicine, Oregon Health Sciences University, Portland 97201.
American Journal of Obstetrics and Gynecology
|May 1, 1988
Summary
Inulin transfer across the placenta was studied in pregnant patients. The placental barrier allows lipid-insoluble molecules between 1350 and 5200 daltons to pass, proportional to their diffusion in water.
Area of Science:
- Obstetrics and Gynecology
- Pharmacokinetics
- Maternal-Fetal Medicine
Background:
- The placental barrier regulates the transfer of substances between mother and fetus.
- Understanding placental permeability is crucial for drug delivery and assessing fetal exposure.
Purpose of the Study:
- To quantify placental permeability to inulin, a lipid-insoluble molecule.
- To establish the range of molecular weights that can cross the placenta.
Main Methods:
- Inulin was administered to term-gestation patients prior to cesarean section.
- Inulin concentrations were measured in maternal plasma, fetal plasma, and amniotic fluid.
- Amniotic fluid volume was assessed via ultrasound; fetal distribution volume was estimated.
Main Results:
- Mean placental permeability to inulin was determined to be 0.15 microliter/(s.g).
- This finding, along with prior cyanocobalamin data, suggests a molecular weight range of 1350-5200 daltons for placental transfer.
- Permeability for lipid-insoluble molecules in this range correlates with their diffusion coefficients in water.
Conclusions:
- The placenta exhibits size-dependent permeability for lipid-insoluble molecules within a specific molecular weight range.
- Placental transfer of molecules is primarily governed by diffusion rates for those within the 1350-5200 dalton range.