title: Estrogen regulation and ion dependence of taurine uptake by MCF-7 human breast cancer cells.
abstract: It has been reported that estrogen receptor-positive MCF-7 cells express TauT, a Na(+)-dependent taurine transporter. However, there is a paucity of information relating to the characteristics of taurine transport in this human breast cancer cell line. Therefore, we have examined the characteristics and regulation of taurine uptake by MCF-7 cells. Taurine uptake by MCF-7 cells showed an absolute dependence upon extracellular Na(+). Although taurine uptake was reduced in Cl(-) free medium a significant portion of taurine uptake persisted in the presence of NO(3) (-). Taurine uptake by MCF-7 cells was inhibited by extracellular beta-alanine but not by L-alanine or L-leucine. 17β-estadiol increased taurine uptake by MCF-7 cells: the V(max) of influx was increased without affecting the K(m). The effect of 17β-estradiol on taurine uptake by MCF-7 cells was dependent upon the presence of extracellular Na(+). In contrast, 17β-estradiol had no significant effect on the kinetic parameters of taurine uptake by estrogen receptor-negative MDA-MB-231 cells. It appears that estrogen regulates taurine uptake by MCF-7 cells via TauT. In addition, Na(+)-dependent taurine uptake may not be strictly dependent upon extracellular Cl(-).
authors.affiliation: Strathclyde Institute of Pharmacy and Biomedical Sciences, Royal College, University of Strathclyde, 204 George Street, Glasgow, UK. G1 1XW, david.shennan@strath.ac.uk
authors.forename: David B
authors.initials: DB
authors.lastname: Shennan
authors.forename: Jean
authors.initials: J
authors.lastname: Thomson
mesh_terms: D001943:Breast Neoplasms / Q000378:metabolism*; D002712:Chlorides / Q000494:pharmacology; D004958:Estradiol / Q000494:pharmacology; D004967:Estrogens / Q000494:pharmacology*; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D005260:Female; D006801:Humans; D007477:Ions; D007700:Kinetics; D007930:Leucine / Q000494:pharmacology; D061986:MCF-7 Cells; D012964:Sodium / Q000494:pharmacology; D013379:Substrate Specificity / Q000187:drug effects; D013654:Taurine / Q000378:metabolism*; D015091:beta-Alanine / Q000494:pharmacology
chemical_list: D002712:Chlorides; D004967:Estrogens; D007477:Ions; D015091:beta-Alanine; D013654:Taurine; D004958:Estradiol; D012964:Sodium; D007930:Leucine