Relation of Extracellular Magnesium to the Cardiac Function and Calcium Content of Working Perfused Rat Heart

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The effect of changing extracellular free Mg ([Mg^<2+>]_o) on cardiac function and intracellualr Mg and Ca content was studied in working perfused rat heart. Total intracellular Ca content decreased linearly from 0.85 to 0.43 μmole/ml intracellular H_2O as [Mg^<2+>]_o increased from 0 to 2 mM in the linear relationship: Total intracellular Ca=0.82-0.20 [Mg^<2+>]_o (1) In contrast, total intracellular Mg content reached a maximum of 18 μmol/ml intracellular H_2O at the physiologically normal [Mg^<2+>]_o of 0.5 mM in a third degree polynomial relationship: Total intracellular Mg=15.7+10.2 [Mg^<2+>]_o-12.2 [Mg^<2+>]_o^2+3.6 [Mg^<2+>]_o^3 (2) Paralleling the maximum in total intracellular Mg content was dP/dt, cardiac work and cardiac efficiency at 0.5 mM [Mg^<2+>]_o. Increasing [Mg^<2+>]_o, cardiac contractility decreased but cardiac O_2 consumption didn't decrease, and cardiac efficiency was the best at 0.5 mM [Mg^<2+>]_o. It is concluded that maximum cardiac efficiency and dP/dt was attained at a physiologically normal [Mg^<2+>]_o of about 0.5 mM and was related to maximal total intracellular Mg, whereas total intracellular Ca decreased linearly with increasing [Mg^<2+>]_o.
北里大学の論文
1994-12-31