Intracellular Mg2+ concentrations following metabolic inhibition in opossum kidney cells.
Intracellular magnesium is associated with intracellular ATP concentrations as Mg-ATP2- and is involved with many enzymes in energy utilization. Intracellular Mg2+ has also been postulated to be involved with various Ca2+ actions. We determined adenine nucleotide concentrations (ATP, ADP and AMP) by HPLC and the associated changes in intracellular free Mg2+ ([Mg2+]i) by fluorescent methods in an epithelial cell line (opossum kidney cells). CCCP (a mitochondrial uncoupler), iodoacetate and amobarbital resulted in marked and rapid falls in [ATP]i with disproportionate increases in [Mg2+]i. These studies indicate that we are able to distinguish Mg2+ movements from Ca2+ by fluorescent techniques and suggests that intracellular regulation of [Mg2+]i is distinctive from those of [Ca2+]i. As CCCP plus amobarbital are reversible, we removed these inhibitors and tested the effect of Mg(2+)-availability on ATP depletion and recovery. The response of magnesium-depleted cells (basal [Mg2+]i 231 +/- 10 microM) following inhibitor-induced energy depletion and ATP recovery were similar to control cells. Accordingly, intracellular [Mg2+]i does not appear to be a limiting factor in ATP regeneration following removal of the chemical hypoxic insult. Finally, exogenous application of Na2ATP2- altered intracellular energy levels in normal and energy depleted cells but was without effect on [Mg2+]i. These studies suggest that intracellular ATP levels do not directly alter intracellular [Mg2+]i control and, in turn, intracellular free Mg2+ is not a limiting factor in ATP regeneration following energy depletion with chemical hypoxia.
Li
H Y
HY
Department of Medicine, University of British Columbia, University Hospital, Vancouver, Canada.
Dai
L J
LJ
Krieger
C
C
Quamme
G A
GA
D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester / Q000494:pharmacology; D000227:Adenine Nucleotides / Q000032:analysis; D000255:Adenosine Triphosphate / Q000378:metabolism* / Q000494:pharmacology; D000654:Amobarbital / Q000494:pharmacology; D000818:Animals; D002118:Calcium / Q000032:analysis; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone / Q000494:pharmacology; D002460:Cell Line / Q000187:drug effects; D003600:Cytosol / Q000378:metabolism; D006019:Glycolysis; D007668:Kidney / Q000378:metabolism*; D008274:Magnesium / Q000032:analysis* / Q000502:physiology; D008928:Mitochondria / Q000378:metabolism; D009893:Opossums; D013997:Time Factors
D000227:Adenine Nucleotides; D002258:Carbonyl Cyanide m-Chlorophenyl Hydrazone; D001498:3-Pyridinecarboxylic acid, 1,4-dihydro-2,6-dimethyl-5-nitro-4-(2-(trifluoromethyl)phenyl)-, Methyl ester; D000255:Adenosine Triphosphate; D000654:Amobarbital; D008274:Magnesium; D002118:Calcium