Abstrakt
The mechanisms of Cl- transfer across the rat placenta have been investigated. Clearance across the intact placenta from mother to fetus (m-->f) of Cr-51-EDTA (paracellular diffusion marker) and Cl-36(-) (K-mf) was 1.9 +/- 0.1 and 37.3 +/- 4.1 mu l/min, respectively (mean +/- SE, n = 10), the large difference indicating that most mtf transfer of Cl- is transcellular.
The clearance of Cl-36(-) 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 K-mf of Cl-36(-) was not inhibited by anoxia and had a low temperature quotient (Q(10) 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-. Cl-36(-) could be displaced from the transporter on the maternal side by other anions with the following order of affinity: Cl- approximate to NO3- > Br- > lactate(-) much greater than gluconate.
It is concluded that most of the Cl- transfer across the rat placenta is effected by an anion exchanger.