title: Elevation of extracellular magnesium rapidly raises intracellular free Mg2+ in human aortic endothelial cells: is extracellular Mg2+ a regulatory cation?
abstract: Extracellular magnesium ions [Mg2+]o are known to regulate functions of endothelial cells, but whether [Mg2+]o can alter intracellular free ionized magnesium [Mg2+]i in these cells remains unknown. The present studies, using digital imaging microscopy and the Mg2+ fluorescent probe, mag-fura-2, determined effects of elevation of [Mg2+]o on [Mg2+]i in cultured human aortic endothelial cells. With normal Mg2+(1.2 mM)-containing incubation media, [Mg2+]i was 0.51+/-0.04 mM with a heterogeneous distribution. The ratio of [Mg2+]i/[Mg2+]o was 0.52+/-0.07. Elevation of [Mg2+]o up to 4.8 mM increased [Mg2+]i to 0.80+/-0.07 mM in 2-10 min and lowered the ratio of [Mg2+]i/[Mg2+]o to 0.16+/-0.02. Irrespective of the observed increments of [Mg2+]i, a subcellular heterogeneous distribution of [Mg2+]i was always evident in all cells tested. Our results suggest that [Mg2+]o can regulate [Mg2+]i more rapidly than heretofore believed, supporting the hypothesis that extracellular Mg2+ can exert regulatory effects on endothelial cell functions and probably act as extracellular regulatory cations
authors.affiliation: Department of Physiology, State University of New York, Health Science Center at Brooklyn, NY 11203, USA.
authors.forename: A
authors.initials: A
authors.lastname: Zhang
authors.forename: B T
authors.initials: BT
authors.lastname: Altura
authors.forename: B M
authors.initials: BM
authors.lastname: Altura
mesh_terms: D002478:Cells, Cultured; D042783:Endothelial Cells / Q000502:physiology*; D006801:Humans; D007424:Intracellular Fluid / Q000737:chemistry; D007477:Ions; D008274:Magnesium / Q000737:chemistry / Q000378:metabolism*
chemical_list: D007477:Ions; D008274:Magnesium