title: Free magnesium concentration in isolated rabbit hearts subjected to high dose isoproterenol infusion: a 31P NMR study.
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.
authors.affiliation: Institut d'éducation physique et de réadaptation, Louvain-la-Neuve, Belgium.
authors.forename: I
authors.initials: I
authors.lastname: Mottet
authors.forename: J F
authors.initials: JF
authors.lastname: Goudemant
authors.forename: M
authors.initials: M
authors.lastname: Francaux
authors.forename: R
authors.initials: R
authors.lastname: Demeure
authors.forename: X
authors.initials: X
authors.lastname: Sturbois
mesh_terms: D000255:Adenosine Triphosphate / Q000378:metabolism; D000318:Adrenergic beta-Agonists / Q000494:pharmacology*; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D006339:Heart Rate / Q000187:drug effects; D006863:Hydrogen-Ion Concentration; D007545:Isoproterenol / Q000494:pharmacology*; D008274:Magnesium / Q000378:metabolism*; D008275:Magnesium Deficiency / Q000175:diagnosis*; D009682:Magnetic Resonance Spectroscopy; D009206:Myocardium / Q000378:metabolism*; D010758:Phosphorus; D011817:Rabbits; D013997:Time Factors
chemical_list: D000318:Adrenergic beta-Agonists; D010758:Phosphorus; D000255:Adenosine Triphosphate; D008274:Magnesium; D007545:Isoproterenol