title: Enhanced sodium-dependent extrusion of magnesium in mutant cells established from a mouse renal tubular cell line.
abstract: To study the regulatory mechanisms of intracellular Mg(2+) concentration ([Mg(2+)](i)) in renal tubular cells as well as in other cell types, we established a mutant strain of mouse renal cortical tubular cells that can grow in culture media with very high extracellular Mg(2+) concentrations ([Mg(2+)](o) > 100 mM: 101Mg-tolerant cells). [Mg(2+)](i) was measured with a fluorescent indicator furaptra (mag-fura 2) in wild-type and 101Mg-tolerant cells. The average level of [Mg(2+)](i) in the 101Mg-tolerant cells was kept lower than that in the wild-type cells either at 51 mM or 1 mM [Mg(2+)](o). When [Mg(2+)](o) was lowered from 51 to 1 mM, the decrease in [Mg(2+)](i) was significantly faster in the 101Mg-tolerant cells than in the wild-type cells. These differences between the 101Mg-tolerant cells and the wild-type cells were abolished in the absence of extracellular Na(+) or in the presence of imipramine, a known inhibitor of Na(+)/Mg(2+) exchange. We conclude that Na(+)-dependent Mg(2+) transport activity is enhanced in the 101Mg-tolerant cells. The enhanced Mg(2+) extrusion may prevent [Mg(2+)](i) increase to higher levels and may be responsible for the Mg(2+) tolerance.
authors.affiliation: Dept. of Physiology, Tokyo Medical Univ., 6-1-1 Shinjuku, Shinjuku-ku, Tokyo 160-8402, Japan. masaru@tokyo-med.ac.jp
authors.forename: Masaru
authors.initials: M
authors.lastname: Watanabe
authors.forename: Masato
authors.initials: M
authors.lastname: Konishi
authors.forename: Ichiro
authors.initials: I
authors.lastname: Ohkido
authors.forename: Senya
authors.initials: S
authors.lastname: Matsufuji
mesh_terms: D000818:Animals; D017920:Antiporters / Q000037:antagonists & inhibitors / Q000235:genetics / Q000378:metabolism*; D002460:Cell Line; D003470:Culture Media; D005110:Extracellular Space / Q000187:drug effects / Q000378:metabolism; D005456:Fluorescent Dyes; D016257:Fura-2 / Q000031:analogs & derivatives; D007099:Imipramine / Q000494:pharmacology; D007684:Kidney Tubules / Q000166:cytology / Q000378:metabolism* / Q000648:ultrastructure; D008274:Magnesium / Q000378:metabolism*; D051379:Mice; D008858:Microscopy, Phase-Contrast; D009154:Mutation; D012964:Sodium / Q000502:physiology*
chemical_list: D017920:Antiporters; D003470:Culture Media; D005456:Fluorescent Dyes; C046250:sodium-magnesium antiporter; C058776:2-(2-(5-carboxy)oxazole)-5-hydroxy-6-aminobenzofuran-N,N,O-triacetic acid; D012964:Sodium; D008274:Magnesium; D007099:Imipramine; D016257:Fura-2