Regulation of taurine transport at the blood-placental barrier by calcium ion, PKC activator and oxidative stress conditions

BACKGROUND: In the present study, we investigated the changes of uptake and efflux transport of taurine under various stress conditions using rat conditionally immortalized syncytiotrophoblast cell line (TR-TBT cells), as in vitro blood-placental barrier (BPB) model. METHODS: The transport of taurine in TR-TBT cells were characterized by cellular uptake study using radiolabeled taurine. The efflux of taurine was measured from the amount of radiolabeled taurine remaining in the cells after the uptake of radiolabeled taurine for 60 min. RESULTS: Taurine uptake was significantly decreased by phosphorylation of protein kinase C (PKC) activator in TR-TBT cells. Also, calcium ion (Ca(2+)) was involved in taurine transport in TR-TBT cells. Taurine uptake was inhibited and efflux was enhanced under calcium free conditions in the cells. In addition, oxidative stress induced the change of taurine transport in TR-TBT cells, but the changes were different depending on the types of oxidative stress inducing agents. Tumor necrosis factor-α (TNF-α), lipopolysaccharide (LPS) and diethyl maleate (DEM) significantly increased taurine uptake, but H(2)O(2) and nitric oxide (NO) donor decreased taurine uptake in the cells. Taurine efflux was down-regulated by TNF-α in TR-TBT cells. CONCLUSION: Taurine transport in TR-TBT cells were regulated diversely at extracellular Ca(2+) level, PKC activator and oxidative stress conditions. It suggested that variable stresses affected the taurine supplies from maternal blood to fetus and taurine level of fetus.