title: Cytosolic free magnesium concentration in cultured chick heart cells.
abstract: Cytosolic free magnesium (Mgi) was measured in embryonic chick heart cells loaded with one of two newly developed 19F nuclear magnetic reasonance (NMR)-sensitive magnesium chelators, 4-methyl,5-fluoro-2-aminophenol-N,N,O-triacetate (MF-APTRA) and 5-fluoro-2-aminophenol-N,N,O-triacetate (5F-APTRA). The cells, embedded in strands of collagen, were superfused at a rate that allowed for solution changes in 2 min. In this preparation 19F- and 31P-NMR spectra were stable for at least 3.5 h. Because Na-coupled Mg countertransport may be a possible mechanism of Mg transport, in some experiments extracellular Na was reduced to 1 mM (choline substituted). This manipulation caused a 2.5-fold increase in Mgi from the basal level of 0.56 mM. A significant proportion of this increase in Mgi could be secondary to an increase in Cai that occurs with low extracellular Na (Nao) perfusion (Nai-Cao exchange). Perfusing cells with nominally Ca-free, 1 mM Na salt solution substantially attenuated the increase in Mgi that occurred with Ca present (1.25 mM) in the low Na (1 mM) solution. Furthermore, perfusion with 1 mM Na, Mg-free salt solution caused a 1.5-fold increase in Mgi, which cannot be attributable to Nai-Mgo exchange. Therefore attempts to describe the regulation of Mgi in heart cells must differentiate between the effects of Nai-Mgo exchange and competition for binding sites that are secondary to stimulation of ion gradient-coupled mechanisms.
authors.affiliation: Department of Cell Biology, Duke University Medical Center, Durham, North Carolina 27710.
authors.forename: S
authors.initials: S
authors.lastname: Rotevatn
authors.forename: E
authors.initials: E
authors.lastname: Murphy
authors.forename: L A
authors.initials: LA
authors.lastname: Levy
authors.forename: B
authors.initials: B
authors.lastname: Raju
authors.forename: M
authors.initials: M
authors.lastname: Lieberman
authors.forename: R E
authors.initials: RE
authors.lastname: London
mesh_terms: D000627:Aminophenols; D000818:Animals; D001667:Binding, Competitive; D002118:Calcium / Q000378:metabolism; D002478:Cells, Cultured; D002614:Chelating Agents; D002642:Chick Embryo; D003600:Cytosol / Q000378:metabolism*; D006321:Heart / Q000196:embryology; D008274:Magnesium / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy; D009206:Myocardium / Q000378:metabolism* / Q000648:ultrastructure; D009994:Osmolar Concentration; D012964:Sodium / Q000008:administration & dosage / Q000378:metabolism / Q000494:pharmacology
chemical_list: D000627:Aminophenols; D002614:Chelating Agents; C060215:5-fluoro-2-aminophenol-N,N,O-triacetate; C060214:4-methyl-5-fluoro-2-aminophenol-N,N,O-triacetate; D012964:Sodium; D008274:Magnesium; D002118:Calcium