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  • Title: Free magnesium concentration in isolated rabbit hearts subjected to high dose isoproterenol infusion: a 31P NMR study.
    Author: Mottet I, Goudemant JF, Francaux M, Demeure R, Sturbois X.
    Journal: Can J Physiol Pharmacol; 1997 Aug; 75(8):1015-21. PubMed ID: 9360017.
    Abstract:
    The hypothesis of magnesium deficiency in isoproterenol (ISO) induced myocardial injury has been investigated by 31P nuclear magnetic resonance spectroscopy. High energy phosphate concentrations, pHi, and intracellular free magnesium concentration ([Mg2+]i) were measured in isolated rabbit hearts perfused at constant flow and subjected to 10(-6)M isoproterenol during 30 min. Recent calibrations were used for [Mg2+]i measurements, and uncertainties on [Mg2+]i estimated values were calculated. During isoproterenol infusion, pHi, [PCr], and [ATP] decreased, while [P(i)] increased. When it was stopped, [PCr] completely repleted, whereas only a partial restoration was observed for pHi and [P(i)]. A rise of end-diastolic pressure and perfusion pressure expressed a contracture, concomitant with a lack of [ATP] recovery, which remained at 59 +/- 13% of the rest value. These results establish that 10(-6) M isoproterenol caused severe myocardial injury. [Mg2+]i increased from 0.70 mM at rest to 0.88 mM at the end of the isoproterenol period. Considering the estimated uncertainties on the [Mg2+]i values, this increase was not significant. After isoproterenol infusion, [Mg2+]i progressively decreased to reach 0.72 mM at 45 min recovery. It is concluded that isoproterenol myocardial toxicity may not be related to [Mg2+]i deficiency.
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