AJP - Cell Physiology, Vol 236, Issue 1 47-C52, Copyright © 1979 by American Physiological Society
Placental transfer of water and nonelectrolytes during a single circulatory passage
J. M. Bissonnette, J. Z. Cronan, L. L. Richards and W. K. Wickham
A bolus of a 14C-labeled nonelectrolyte and tritiated water was injected
into the maternal arterial system supplying the uterine circulation. Blood
was sampled immediately on the fetal side of the placenta from the
umbilical vein. A placental transfer index (PTI) was calculated from the
ratio of the tracers in the fetal blood divided by the ratio of the tracers
in the injectate. Placental transfer was measured for 11 nonelectrolytes in
anesthetized guinea pigs and 8 nonelectrolytes in unanesthetized sheep.
Placental transfer in both species was determined by molecular weight and
lipid solubility. The PTI measured for the lipophilic solutes antipyrine
and 1,6-hexanediol were less than 1, and those for methanol and ethanol
were greater than 1. We conclude that placental transfer for water and
small (mol wt less than 200) lipid-soluble nonelectrolytes is limited by
diffusion as well as by blood flow.
