Zusammenfassung
OBJECTIVE: Magnesium regulates a large number of cellular processes.
Small changes in intracellular free Mg(2+) (Mg(2+)(i)) may have
important effects on cardiac excitability and contractility. We investigated
the effects of Mg(2+)(i) on cardiac excitation-contraction coupling.
METHODS: We used our ionic-metabolic model that incorporates equations
for Ca(2+) and Mg(2+) buffering and transport by ATP and ADP and
equations for MgATP regulation of ion transporters (Na(+)-K(+) pump,
sarcolemmal and sarcoplasmic Ca(2+) pumps). RESULTS: Model results
indicate that variations in cytosolic Mg(2+) level might sensitively
affect diastolic and systolic Ca(2+), sarcoplasmic Ca(2+) content,
Ca(2+) influx through L-type channels, efficiency of the Na(+)/Ca(2+)
exchanger and action potential shape. The analysis suggests that
the most important reason for the observed effects is a modified
normal function of sarcoplasmic Ca(2+)-ATPase pump by altered diastolic
MgATP levels. CONCLUSION: The model is able to reproduce qualitatively
a sequence of events that correspond well with experimental observations
during cardiac excitation-contraction coupling in mammalian ventricular
myocytes.
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