Beneficial effect of magnesium on the isolated perfused rat heart during reperfusion after ischaemia: comparison between pre-ischaemic and post-ischaemic administration of magnesium.
The effect of high concentration of magnesium on both mechanical dysfunction and metabolic damage after ischaemia-reperfusion was studied in isolated rat hearts. The heart was perfused by the Langendorff's technique at a constant flow (10 ml/min) with modified Krebs-Henseleit solution and driven at 300 beats/min. The heart was made ischaemic by reducing the flow to 0 ml/min for 25 min, and then reperfused at the constant flow for 15 min. MgSO4 was added to the perfusate for 5 min before the onset of ischaemia, or after the end of ischaemia (after the onset of reperfusion). Ischaemia-reperfusion produced both mechanical dysfunction (as evidenced by an increase in the left ventricular end diastolic pressure and a decrease in the left ventricular developed pressure) and metabolic damage [as evidenced by a decrease in the myocardial adenosine triphosphate (ATP)]. When 15 mmol/l MgSO4 was given before ischaemia, there was no appreciable recovery of mechanical function, whereas when given after ischaemia (during reperfusion), there was a marked recovery of mechanical function. Lower concentrations (10 or 5 mmol/l) of MgSO4 given after ischaemia recovered the mechanical function concentration-dependently. The beneficial effect of 15 mmol/l MgSO4 was minimized by the coexistence of 4.5 mmol/l CaCl2 in the reperfusion solution. The decrease in the myocardial level of ATP induced by ischaemia-reperfusion was attenuated by 15 mmol/l MgSO4 given in the reperfusion solution. These results suggest that high Mg2+ is effective in attenuating both functional and metabolic damage of the post-ischaemic heart, provided it is given after ischaemia.
Hara
A
A
Department of Pharmacology, Asahikawa Medical College, Japan.
Matsumura
H
H
Abiko
Y
Y
D000255:Adenosine Triphosphate / Q000494:pharmacology; D000818:Animals; D001794:Blood Pressure / Q000187:drug effects; D003327:Coronary Disease / Q000188:drug therapy* / Q000503:physiopathology; D004734:Energy Metabolism / Q000187:drug effects; D006321:Heart / Q000187:drug effects*; D006334:Heart Function Tests; D066298:In Vitro Techniques; D008274:Magnesium / Q000627:therapeutic use*; D008297:Male; D015425:Myocardial Reperfusion; D009206:Myocardium / Q000378:metabolism; D010725:Phosphocreatine / Q000494:pharmacology; D051381:Rats; D011919:Rats, Inbred Strains
D010725:Phosphocreatine; D000255:Adenosine Triphosphate; D008274:Magnesium