AJP - Regulatory, Integrative and Comparative Physiology, Vol 270, Issue 5 984-R989, Copyright © 1996 by American Physiological Society
Effect of NaCl load administered to the fetus on the bidirectional movement of 51Cr-EDTA across rat placenta
J. Stulc and B. Stulcova
Department of Pharmacology, Second Faculty of Medicine, Charles University, Prague, Czech Republic.
A hypothesis that, in the rat, fluid circulates across the placenta, with
circulation being maintained by active transport of Na+ from mother to
fetus, has been tested. Transfer of 51Cr-EDTA from mother to fetus and from
fetus to mother has been measured and the respective unidirectional
transfer constants, Kmf and Kfm, have been calculated. Immediately before
the transfer measurement, the fetuses were injected intravenously with 10
microliters of isotonic glucose (controls); with 30 or 300 microliters of
isotonic saline; or with 10, 30, or 60 microliters of 9% NaCl. In controls,
Kmf of 51Cr-EDTA was 2.0 +/- 0.6 microliters/min, and Kfm was 4.3 +/- 1.0
microliters/min. Injecting the fetus with NaCl had no effect on Kmf,
whereas the Kfm was increased significantly in a dose-dependent way. In
other experiments, 51Cr-EDTA was injected into nephrectomized maternal
animals, and the radioactivity of maternal and fetal plasma was followed
for 30 h. The time course of fetal plasma radioactivity supported the
thesis that the transfer of 51Cr-EDTA across the rat placenta is highly
asymmetrical.
