Cardioprotective and Anti-arrhythmic Effects of Magnesium Pretreatment Against Ischaemia/Reperfusion Injury in Isoprenaline-Induced Hypertrophic Rat Heart.

Abstract

The effects of magnesium (Mg2+) on ischaemic complications of pathological cardiac hypertrophy are unclear. In this study, we investigated effects of Mg2+ pretreatment on ischaemia/reperfusion (I/R) injury in isoprenaline (ISO)-induced hypertrophic hearts. Wistar rats were treated for 7days with different combinations of ISO (1.25mg/kg) subcutaneously, MgSO4 (270mg/kg) intraperitoneally, or vehicle (saline). On the eighth day, hearts were either subjected to regional I/R during Langendorff perfusion or histologically stained with haematoxylin and eosin and Masson's trichrome. Haemodynamic and electrocardiographic parameters were recorded using the PowerLab data-acquisition system. Infarcts were identified by triphenyltetrazolium chloride staining. Plasma Mg2+ was measured using photometric assays. Mg2+ pretreatment significantly decreased I/R-induced infarct size (p=0.001) and the overall arrhythmia score (p<0.001) of I/R-induced ventricular ectopics, ventricular tachycardia, and ventricular fibrillation in hypertrophic hearts, but not non-hypertrophied hearts. Mg2+ also improved post-I/R left ventricular developed pressure in hypertrophic hearts. However, Mg2+ did not reverse the ISO-induced myocyte thickening and interstitial fibrosis or increases in heart weight. Plasma Mg2+ was not different among treatment groups. These results suggest that Mg2+ pretreatment may protect against I/R-induced injury and malignant arrhythmias in hypertrophic hearts, possibly via mechanisms unrelated to long-lasting changes in plasma Mg2+ or prevention of structural changes such as fibrosis.