Paracellular urate transport in the placenta

Abstract

Serum urate level is elevated in pregnancy induced hypertension or multiple pregnancies; however, how urate is handled in the placenta is still unknown. Blood samples from pregnant women who underwent caesarian section were examined. There were no significant differences in serum urate levels between maternal and umbilical cord blood, suggesting that urate is freely moved through the placenta. By RT‐PCR, mRNA of possible urate transporters, OAT4, OAT10, URATv1 and ABCG2, was expressed in the placenta and BeWo cells, a cell line derived from choriocarcinoma. BeWo cells did not take up urate despite the presence of urate transporters. Instead, urate moved through BeWo cell monolayers from apical to basal as well as reverse direction when the cells were incubated at 37 or 4 degree, suggesting that urate moves through paracellular route. Several claudins were commonly expressed in BeWo cells and in the placenta by RT‐PCR and LC/MS. It is likely that such claudin(s) are responsible for paracellular transport of urate in the placenta.