PLASMA-MEMBRANE FATTY-ACID-BINDING PROTEIN (FABP(PM)) IS EXCLUSIVELY LOCATED IN THE MATERNAL FACING MEMBRANES OF THE HUMAN PLACENTA

We reported earlier the presence of a 40 kDa plasma membrane fatty acid-binding protein (FABP(pm)) in human placenta, This protein is thought to be involved in the sequestration of unesterified free fatty acids bound to albumin from the maternal plasma for delivery to the fetus, However its location in human placental syncytiotrophoblasts is not known, These cells are bipolar; one side facing maternal circulation (microvillous membranes), and the other side facing fetal circulation (basal membranes), Therefore, it is important to resolve the location of this protein in trophoblast membranes in order to understand fatty acid transport and metabolism in human placenta, Isolated plasma membranes vesicles were prepared respectively from the maternal facing microvillous and fetal facing surface of the human full-term placental syncytiotrophoblast. Using these membrane preparations, fatty acid binding activity, the polyacrylamide gel electrophoresis radiobinding assay for FABP(pm), and Western blot analysis of FABP(pm) were carried out to determine the location of this protein in these membranes. Based on the above studies me conclude that the FABP(pm) is located exclusively in the microvillous membranes, Since FABP(pm) may be responsible for FFA uptake, its location in the microvillous membranes favours the unidirectional flow of maternal FFA to the fetus.