AJP - Regulatory, Integrative and Comparative Physiology, Vol 271, Issue 5 1107-R1114, Copyright © 1996 by American Physiological Society
Transfer of Cl- across placenta of anesthetized rat
J. Stulc, B. Stulcova, S. Husain and C. P. Sibley
Department of Pharmacology, Second Faculty of Medicine, Charles University, Prague, Czech Republic.
The mechanisms of Cl- transfer across the rat placenta have been
investigated. Clearance across the intact placenta from mother to fetus
(m-->f) of 51Cr-EDTA (paracellular diffusion marker) and 36Cl- (Kmf) was
1.9 +/- 0.1 and 37.3 +/- 4.1 microliters/min, respectively (mean +/- SE, n
= 10), the large difference indicating that most m-->f transfer of Cl-
is transcellular. The clearance of 36Cl- across the dually perfused
placenta in m-->f and fetal-to-maternal directions was symmetrical and
highly sensitive to the anion-exchange inhibitor
4,4'-diisothiocyanostilbene-2,2'-disulfonic acid (0.1 mM). The Kmf of 36Cl-
was not inhibited by anoxia and had a low temperature quotient (Q10 between
32 and 37 degrees C was 1.52). The m --> f transfer of Cl- seemed to be
fully saturated at physiological concentrations of Cl-. 36Cl- could be
displaced from the transporter on the maternal side by other anions with
the following order of affinity: Cl- approximately NO3- > Br- >
lactate- >> gluconate. It is concluded that most of the Cl- transfer
across the rat placenta is effected by an anion exchanger.
