Urea transport in normal and preeclamptic placentas

DAMIANO ALICIA E; ZOTTA ELSA; IBARRA CRISTINA

San Pablo

Simposio; I Latin-American Symposium on Maternal-Fetal Interaction and Placenta:Basic & Clinical Research; 2003

Placenta Association of the Americas- Grupo Latinoamericano de placenta

Normal fetal growth and development is critically dependent on sufficient transport of of nutrients, metabolites, ions and water across the placenta. Because of the syncytiotrophoblast of human term placenta (hST) is a continuous, multinucleated structure with minimal tight junctions, the transport from mother to fetus should take place primarily via transcellular routes. However, the possibility exists that wide, nonspecific, paracellular channels, allowing the passage of large hydrophilic molecules, may also be present. Transcellullar flux of urea may be facilitated by aquagliceroporins or/ and by urea transporters (UT). Previously we have reported the different expression of aquaglyceroporins in hST. These proteins allow the rapid passage of water, urea, glycerol and a wide variety of non-charged solutes. Recently, we have reported the expression and localization of urea transporter type A (UT-A) in normal placenta from first and third trimester, by RT-PCR, immunoblotting, and immunocytochemistry. We have also observed that the expression of UT-A is altered in preeclamptic placentas. UT-A expression is stronger in preeclampsia than in normal pregnancies. In order to evaluate their functionality, explants from normal and preeclamptic placentas were cultured in DMEM for 48 h. Undirectional fluxes of 14C-urea were measured. The incorporation of 14C-urea in explants from preeclamptic placentas was significantly higher than in normal placentas. In both cases, the uptake was inhibited by phloretin 0,5 mM. These results demonstrate that functional UT-A is present in placental villuous. Further experiments will be needed to elucidate the importance of the urea transporter in the etiology of preeclampsia.