Influence of magnesium sulfate on sizes of myocardial infarction in rabbits

Myocardial infarction was made in open-chest rabbits. Immediatly after the occlusion of the anterior descending branch of left coronary artery (LAD), IO% MgS04 400 mg/kg was iv t0 8 rabbits. The same doses of MgSO, were given 24 and 48 h later. Saline (20 ml) and propranolol (2 mg/kg) were given separately to another 2 groups of rabbits for comparison. The results showed that: (1) The extents of the experimental myocardial infarction werc 14 + 5, 15 + 5 and 22+ 7% for magnesium sulfate (M). propranolol (P) and saline group (NS), respectively. (2) The epicardial ST segment elevation was improved (NST : 8+4, 0.1 + O.11;7+5, 4.0 + 1.8 and 11.2 + 1.5. 7+4. ST : 4.0 + 1.0. 0.4+1.1; 4.8+2.7. 2.4+1.2 and 8+3. 2.7+0.7 for (M), (P) and (NS) 2 and 72 h after LAD). (3) The numbers of pathologic Q wave were decreased (5.6 + 1.8, 5.9+1.9 and 9+3, 9+4 for (M) and (NS) groups 24 and 72 h after LAD). (4) The heart rates were declined (131+10. 138+11 and 163+5 for (M). (P) and (NS), respectively. (5) The ventricular arrhythmia was eliminated in the group treated with (M), as compared with NS, P<0.05. To conclude, the (M) treatment is apparently beneficial in reducing the size of the experimental myocardial infarction.