uptake of dehydroepiandrosterone3sulfate by isolated trophoblasts from human term placenta jeg3 bewo jar bhk cells and bhk cells transfected with human sterylsulfatasecdna the human placenta lacks the enzyme 17alphahydroxylase1720lyase and is thus unable to convert cholesterol into estrogens therefore estrogen synthesis of trophoblast cells depends on the supply of precursors such as dehydroepiandrosterone3sulfate dheas and 16alphahydroxydehydroepiandrosterone3sulfate by maternal and fetal blood to investigate the cellular internalisation of these anionic hydrophilic precursors the uptake of 3h35sdheas and 3htaurocholate by isolated cytotrophoblasts cells of choriocarcinoma cell lines jeg3 bewo jar bhk and bhk cells transfected with human sterylsulfatasecdna bhksts cells was studied furthermore the activity of sterylsulfatase of these cells in suspension and in corresponding cell homogenate was measured during the first 5 min of incubation with 3hdheas or 35sdheas radioactivity of cytotrophoblasts increased significantly while radioactivity of jeg3 jar bhk and bhksts cells did not increase radioactivity of bewo cells increased slightly for all cell types there was no significant difference for uptake of either substrate during incubation with 3htaurocholate radioactivity of cytotrophoblasts did not increase sterylsulfatase activity of cytotrophoblast homogenate was significantly lower than that of cytotrophoblast suspension sterylsulfatase activity of bhksts jeg3 or bewo cell homogenate was significantly higher than that of the corresponding cell suspension in bhk and jar cells sterylsulfatase activity was not detectable cytotrophoblasts take up dheas without prior hydrolysis bhk bhksts jeg3 and jar cells do not take up and bewo cells slowly take up dheas in cytotrophoblasts extracellular dheas rapidly gains access to intracellular sterylsulfatase while in choriocarcinoma and bhksts cells access of dheas to sterylsulfatase is limited our results indicate that uptake by cytotrophoblasts is mediated by a carrier which is not expressed in choriocarcinoma or bhk cells and which is different from the known taurocholatetransporting organic anion transporting polypetides