Functional and molecular expression of AQP9 channel and UT-A transporter in normal and preeclamptic human placentas.
Transcellular flux of urea across human placenta may be facilitated by aquaglyceroporins and/or by urea transporters (UT). Previously we have reported the presence of AQP3 and AQP9 in the syncytiotrophoblast of human term placenta (hST). In the present study, we detected a significant uptake of water, urea and mannitol sensitive to mercury and phloretin in explants from normal term placenta, which indicates a functional AQP9. In addition, we observed an increase of AQP9 expression in preeclamptic placenta with a lack of functionality of AQP9 for water and mannitol. Our data showed a molecular and functional expression of UT-A in hST from normal and preeclamptic placentas. In the last case, urea uptake sensitive to phloretin and mercury increased and the UT-A protein seems to be augmented. These results suggest that the increase of urea uptake in preeclamptic pregnancies could be attributed to an increase of expression of UT-A more than AQP9 proteins. In conclusion, our results provide new evidences that suggest the involvement of AQP9 and UT-A in the urea excretion mechanism across hST from mother to fetus in physiological conditions. Much further work is needed to define whether the overexpression of AQP9 plays a direct role either in the pathogenesis or in the adaptative response of preeclampsia.
Laboratorio de Fisiopatogenia, Departamento de Fisiología, Facultad de Medicina, Universidad de Buenos Aires, Paraguay 2155, 7mo piso, 1121 Buenos Aires, Argentina.
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Damiano
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Zotta
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Ibarra
D000595:Amino Acid Sequence; D020346:Aquaporins / Q000096:biosynthesis*; D005260:Female; D006651:Histocytochemistry; D006801:Humans; D008353:Mannitol / Q000378:metabolism; D026901:Membrane Transport Proteins / Q000096:biosynthesis*; D008969:Molecular Sequence Data; D010920:Placenta / Q000378:metabolism*; D011225:Pre-Eclampsia / Q000378:metabolism*; D011247:Pregnancy; D014327:Trophoblasts / Q000378:metabolism; D014508:Urea / Q000378:metabolism; D014867:Water / Q000378:metabolism; D000096982:Urea Transporters
D020346:Aquaporins; D008353:Mannitol; D026901:Membrane Transport Proteins; D014508:Urea; D014867:Water; D000096982:Urea Transporters; C109669:AQP9 protein, human