Caffeine decreases intracellular free Mg2+ in isolated adult rat ventricular myocytes.
Caffeine has been extensively used to study intracellular Ca2+ control and contraction-relaxation in cardiomyocytes. The effects of caffeine on intracellular free Mg2+ concentration, [Mg2+]i, were studied in isolated adult rat ventricular myocytes by fluorescent techniques using mag-fura-2. Basal [Mg2+]i was 0.62 +/- 0.02 mM, n = 54, in quiescent cells and 0.73 +/- 0.02 mM, n = 23, in electrically-stimulated adult rat ventricular myocytes. Caffeine, 20 mM, significantly decreased [Mg2+] in both quiescent (-0.17 +/- 0.01 mM) and electrically-stimulated (-0.16 +/- 0.01 mM) adult ventricular myocytes. Ryanodine, a blocker for Ca(2+)-release channels of the sarcoplasmic reticulum, did not have any effect on basal [Mg2+]i, 0.67 +/- 0.02 mM nor on caffeine-induced reduction in [Mg2+]i, -0.16 +/- 0.01 mM in quiescent cardiomyocytes or electrically-stimulated cells; 0.74 +/- 0.03 mM and -0.11 +/- 0.03 mM, respectively. Ruthenium red, an inhibitor of mitochondrial Ca2+ uptake, also failed to alter basal [Mg2+]i, or caffeine-induced reduction in [Mg2+], in either quiescent or electrically-stimulated cells. The effects of caffeine on [Mg2+]i, may be important in considering the use of this drug to study contraction/function studies in heart cells.
Li
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Department of Medicine, University of British Columbia, Vancouver Hospital, Canada.
Quamme
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GA
D000818:Animals; D002110:Caffeine / Q000494:pharmacology*; D002118:Calcium / Q000378:metabolism; D002121:Calcium Channel Blockers / Q000494:pharmacology; D015220:Calcium Channels / Q000187:drug effects / Q000378:metabolism; D002469:Cell Separation; D004558:Electric Stimulation; D004791:Enzyme Inhibitors / Q000494:pharmacology; D005707:Gallic Acid / Q000031:analogs & derivatives / Q000494:pharmacology; D006352:Heart Ventricles; D008274:Magnesium / Q000378:metabolism*; D008929:Mitochondria, Heart / Q000187:drug effects / Q000378:metabolism; D009200:Myocardial Contraction; D009206:Myocardium / Q000166:cytology / Q000378:metabolism*; D051381:Rats; D012430:Ruthenium Red / Q000494:pharmacology; D012433:Ryanodine / Q000494:pharmacology; D012964:Sodium / Q000378:metabolism; D019284:Thapsigargin / Q000494:pharmacology
D002121:Calcium Channel Blockers; D015220:Calcium Channels; D004791:Enzyme Inhibitors; D012430:Ruthenium Red; D012433:Ryanodine; D002110:Caffeine; C006014:8-(N,N-diethylamino)octyl-3,4,5-trimethoxybenzoate; D005707:Gallic Acid; D019284:Thapsigargin; D012964:Sodium; D008274:Magnesium; D002118:Calcium