Water channel proteins AQP3 and AQP9 are present in syncytiotrophoblast ofhuman term placenta

The syncytiotrophoblast of human term placenta (HST) is a continuous, multi nucleated structure with minimal tight junctions, which results from the fu sion of the underlying cytotrophoblast cells. Consequently, the transport o f metabolites, ions and water from mother to fetus could take place primari ly via transcellular routes. Transcellular water flux may be facilitated by aquaporins, membrane proteins functioning as water channels that are widel y expressed in cells and tissues. Here, we report the presence of AQP3 and AQP9 in the apical membranes of HST using RT-PCR, immunoblotting and immuno histochemistry. Since AQP3 is not only a water channels, but also permits t he rapid passage of both urea and glycerol, while AQP9 also mediates the pa ssage of carbamides, polyols, purines, and pyrimidines, we have speculated that these proteins could be involved in the transport of water and solutes from mother to fetus. (C) 2001 Harcourt Publishers Ltd.