Asymmetrical transport of glucose across the in vitro perfused human placenta

The transplacental flux of glucose together with the consumption by the tissue was studied in human term placenta using the dual in vitro perfusion of an isolated cotyledon. The effect of different transplacental glucose gradients going either from the maternal to the foetal side or in the opposite direction was tested. A linear correlation between uptake from the donor circuit as well as transplacental flux and concentration difference of glucose between the two sides was found in both directions. At comparable gradients both uptake and flux were significantly higher with the gradient going from the maternal to the foetal side as compared to the other direction. For the non-metabolizable 2-deoxy-analog of D -glucose no asymmetry of flux was seen. The large fraction of glucose uptake, which is metabolized by placental tissue together with the difference in membrane transport capacity across the microvillous as compared to the basal membrane of the syncytiotrophoblast could be an explanation for the asymmetry in transplacental glucose flux.