The effects of sodium, hydrogen and magnesium ions on mitochondrial calcium sequestration in adult rat ventricular myocytes.
The effect of Na+, H+ and Mg2+ ions on net calcium exchange induced in digitonin-treated myocytes has been investigated. Raising the [Na] from 1.4 to 31.4 mM revealed a sodium-sensitive fraction of net calcium exchange with a K1/2 for Na+ ions of 12 mM, alongside the respiration-dependent accumulation of calcium. An acidosis, but not an alkalosis, was found to depress both of these processes. Mg2+ ions exerted an effect solely on the respiration-dependent calcium sequestration. A simple semi-empirical model based on the experimental data was formulated to assess the effects that altering sarcoplasmic [Na+] and [H+] would have on the calcium-handling properties of cardiac mitochondria. It is concluded that part of the inotropic effects of these ions could be mediated via this organelle.
D000818:Animals; D001692:Biological Transport / Q000187:drug effects; D002118:Calcium / Q000378:metabolism*; D004072:Digitonin / Q000494:pharmacology; D006352:Heart Ventricles / Q000378:metabolism; D006863:Hydrogen-Ion Concentration; D008274:Magnesium / Q000494:pharmacology*; D008929:Mitochondria, Heart / Q000378:metabolism*; D009206:Myocardium / Q000378:metabolism*; D051381:Rats; D012964:Sodium / Q000494:pharmacology*
D012964:Sodium; D008274:Magnesium; D004072:Digitonin; D002118:Calcium