Diffusive transfer of water and glucose across the chorionic plate of the isolated human term placenta

This study investigated systematically the diffusive transfer of water and glucose across the chorionic plate of the human placenta. Isolated sections of human term placentae were perfused at the fetal side (open loop) with m odified Ringer's solution (n=31). An artificial amniotic compartment was cr eated on top of the chorionic plate. H-3- and C-14-labelled tracer pairs we re added (donor side) to the fetal perfusion fluid or to the 'amniotic' flu id. Transfer fractions (TF, ratio of acceptor side to donor side radioactiv ity) were calculated as percentages. TF of water and L-glucose from perfusi on fluid into the 'amniotic' fluid were 3.9 +/- 0.5 per cent (mean +/- SEM) and 1.2 +/- 0.3 per cent after 60 min and significantly different (n = 6). In each sample of the following experiments the transfer fraction of the D -hexose was larger than that of the L-isomer. At 60 min, the TF were 1.6 +/ - 0.2 and 1.1 +/- 0.2 per cent (D-glucose/L-glucose; fetal to amniotic comp artment, n = 8), from amniotic compartment to fetal perfusate 0.6 +/- 0.1 a nd 0.4 +/- 0.1 per cent (D-glucose/L-glucose, n=11), and 0.8 +/- 0.1 and 0. 6 +/- 0.1 per cent (3-O-methyl-D-glucose/L-glucose, n=6). The difference be tween the latter TF lost its significance after cytochalasin B (0.1-0.2 mmo l/l) had been added to the amniotic compartment. It is concluded that a lim ited diffusive pathway across the chorionic plate of the human placenta exi sts and that the transfer of D-glucose depends in part on facilitated diffu sion. (C) 1999 W. B. Saunders Company Ltd.