title: Cytosolic free magnesium levels in ischemic rat heart.
abstract: Changes in cytosolic free magnesium ion concentration (Mgi) during myocardial ischemia were measured by 19F NMR in perfused rat hearts loaded with fluorine-labeled derivatives of the magnesium chelator o-aminophenol-N,N,O-triacetate. The perfused rat hearts were loaded intracellularly with the appropriate magnesium indicator by perfusion with 200-400 ml of Krebs-Henseleit buffer containing 5 microM acetoxymethyl ester of the indicator. Basal Mgi concentrations measured by three different indicators averaged 0.85 +/- 0.10 mM (n = 9) and showed no correlation with the KD of the indicator used. 31P NMR measurements of the magnesium-dependent shift between alpha- and beta-phosphates of ATP demonstrate that there is no measurable lowering of Mgi during loading with fluorinated o-aminophenol-N,N,O-triacetate. Between 10 and 15 min of ischemia, Mgi rose nearly 3-fold to 2.1 +/- 0.4 mM. This increase in Mgi occurred over the same time course as the decrease in ATP. After 20 min of reperfusion with Krebs-Henseleit buffer, Mgi declined to 1.5 +/- 0.5 mM. This sustained elevation of Mgi above basal levels may inhibit calcium release from sarcoplasmic reticulum, thereby contributing to the well documented impairment of mechanical function that occurs after a reversible period of ischemia.
authors.affiliation: Laboratory of Molecular Biophysics, National Institute of Environmental Health Sciences, Research Triangle Park, North Carolina 27709.
authors.forename: E
authors.initials: E
authors.lastname: Murphy
authors.forename: C
authors.initials: C
authors.lastname: Steenbergen
authors.forename: L A
authors.initials: LA
authors.lastname: Levy
authors.forename: B
authors.initials: B
authors.lastname: Raju
authors.forename: R E
authors.initials: RE
authors.lastname: London
mesh_terms: D000085:Acetates; D000627:Aminophenols; D000818:Animals; D002614:Chelating Agents; D003327:Coronary Disease / Q000378:metabolism*; D003600:Cytosol / Q000378:metabolism; D005461:Fluorine; D008274:Magnesium / Q000378:metabolism*; D009682:Magnetic Resonance Spectroscopy / Q000379:methods; D008297:Male; D009206:Myocardium / Q000378:metabolism*; D010477:Perfusion; D051381:Rats; D011919:Rats, Inbred Strains; D012016:Reference Values
chemical_list: D000085:Acetates; D000627:Aminophenols; D002614:Chelating Agents; C027667:2-aminophenol; D005461:Fluorine; D008274:Magnesium