In this study, we have established new syncytiotrophoblast cell lines (TR-TBTs) from the recently developed transgenic rat harboring temperature-sensitive simian virus 40 large T-antigen gene (Tg-rat). Four conditionally immortalized syncytiotrophoblast cell lines (TR-TBT 18d-1∼4) were obtained from pregnant Tg-rats at gestational day 18. These cell lines had a syncytium-like morphology, could be prepared as monolayers, expressed cytokeratins and rat syncytiotrophoblast markers, and exhibited apical or basal GLUT1 localizations and apical GLUT3 localizations. TR-TBTs express large T-antigen and grow well at 33°C with a doubling time of about 30 h. TR-TBTs have processes for the uptake of dehydroepiandrosteron-3-sulfate (DHEAS) and these are predominantly located on the basal side, and this is the first report of an in vitro model of blood placental barrier (BPB) able to incorporate DHEAS. Therefore, TR-TBTs are an appropriate in vitro model for investigating carrier-mediated transport functions at the BPB. Moreover, TR-TBTs express betaine/GABA transporter (GAT-2/BGT-1), concentrative nucleoside transporter 2 (CNT2), equilibrative nucleoside transporter 1 (ENT1), and ENT2 and the expression of these transporters has been reported in blood-brain barrier (BBB). Thus, the expression patterns of nucleoside and neurotransmitter transporters examined are quite similar in both the BPB and BBB.
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