title: Sodium-independent lysine uptake by the BeWo choriocarcinoma cell line.
abstract: Transport of L-lysine by a cultured placental trophoblast cell line was investigated by characterization of L-[3H]lysine uptake. In the mononuclear form of the BeWo clone b30 choriocarcinoma cell, at least two sodium-independent systems are present. Concentration dependence data were fitted by a two system model with Km values (+/- s.e.) of 2 +/- 0.7 and 94 +/- 31 microM and Vmax values (+/- s.e.) of 0.7 +/- 0.3 and 25 +/- 6.0 nM/mg DNA/min. A portion of sodium-independent uptake was inhibited by the sulphydryl modifying reagent N-ethylmaleimide (NEM). Following NEM treatment, the data were fitted by a single system with Km = 10 +/- 2 microM AND Vmax = 5.1 +/- 0.8 nM/mg DNA/min. In the absence of sodium, NEM-resistant uptake was sensitively inhibited by leucine whereas NEM-sensitive uptake was not inhibited by leucine. It is concluded that like placental basal membrane, the mononuclear BeWo cell possesses two sodium-independent L-lysine transport systems. The high-capacity, NEM-sensitive, leucine-insensitive system resembles the widespread system y+. The high-affinity, NEM-resistant, leucine-sensitive system resembles system b(0,+).
authors.affiliation: The Edward Mallinckrodt Department of Pediatrics, St Louis Children's Hospital, Washington University School of Medicine, Missouri 63110, USA.
authors.forename: B A
authors.initials: BA
authors.lastname: Way
authors.forename: T C
authors.initials: TC
authors.lastname: Furesz
authors.forename: J K
authors.initials: JK
authors.lastname: Schwarz
authors.forename: A J
authors.initials: AJ
authors.lastname: Moe
authors.forename: C H
authors.initials: CH
authors.lastname: Smith
mesh_terms: D001693:Biological Transport, Active / Q000187:drug effects; D002822:Choriocarcinoma / Q000378:metabolism*; D004273:DNA, Neoplasm / Q000378:metabolism; D005033:Ethylmaleimide / Q000494:pharmacology; D005260:Female; D006801:Humans; D007700:Kinetics; D008239:Lysine / Q000378:metabolism*; D008431:Maternal-Fetal Exchange; D011247:Pregnancy; D012964:Sodium / Q000378:metabolism; D013439:Sulfhydryl Reagents / Q000494:pharmacology; D014327:Trophoblasts / Q000378:metabolism; D014407:Tumor Cells, Cultured; D014594:Uterine Neoplasms / Q000378:metabolism*
chemical_list: D004273:DNA, Neoplasm; D013439:Sulfhydryl Reagents; D012964:Sodium; D008239:Lysine; D005033:Ethylmaleimide