title: Intracellular pH modulates cytosolic free magnesium in cultured chicken heart cells.
abstract: To assess the role of pH in cellular Mg homeostasis, cytosolic pH (pHi) was manipulated by the NH4Cl prepulse technique; pHi, cytosolic Mg2+ (Mgi), and cytosolic Ca2+ (Cai) were measured fluorometrically in single cultured embryonic chicken heart cells loaded with 2',7'-bis(2-carboxyethyl)-5(6)-carboxyfluorescein (BCECF), FURAPTRA, and fura-2, respectively. The basal values obtained were as follows: pHi = 7.21 +/- 0.10 (n = 7), [Mg]i = 0.51 +/- 0.08 mM (n = 9), [Ca]i = 126 +/- 15 nM (n = 7). When cells were perfused with 10 mM NH4Cl solution for 5 min, a transient alkalinization (0.53 U) of the cytosol was accompanied by a transient decrease (0.12 mM) in [Mg]i and a transient increase (59 nM) in [Ca]i; these changes approached control levels within 5 min. Upon removal of NH4Cl, a transient acidification (0.89 U) of the cytosol was accompanied by a transient increase (0.10 mM) in [Mg]i and a transient increase (125 nM) in [Ca]i; again, these changes returned toward control levels within 5 min. No significant changes in total cell Mg or Ca were observed during these manipulations. NH4Cl-evoked changes in [Mg]i were not altered significantly by either Mg-free or Ca-free conditions. Changes in [Mg]i were inversely correlated with changes in pHi and were not secondary to changes in [Ca]i. The results suggest that pHi modulates Mgi, probably by affecting cytosolic Mg binding and/or the transport of Mg across subcellular organelles.
authors.affiliation: Department of Cell Biology, Duke University Medical Center, Durham 27710.
authors.forename: C C
authors.initials: CC
authors.lastname: Freudenrich
authors.forename: E
authors.initials: E
authors.lastname: Murphy
authors.forename: L A
authors.initials: LA
authors.lastname: Levy
authors.forename: R E
authors.initials: RE
authors.lastname: London
authors.forename: M
authors.initials: M
authors.lastname: Lieberman
mesh_terms: D000643:Ammonium Chloride / Q000494:pharmacology; D000818:Animals; D002478:Cells, Cultured; D002642:Chick Embryo; D003600:Cytosol / Q000378:metabolism*; D005456:Fluorescent Dyes; D006863:Hydrogen-Ion Concentration; D007425:Intracellular Membranes / Q000378:metabolism*; D008274:Magnesium / Q000378:metabolism*; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D009994:Osmolar Concentration; D012964:Sodium / Q000494:pharmacology
chemical_list: D005456:Fluorescent Dyes; D000643:Ammonium Chloride; D012964:Sodium; D008274:Magnesium