Magnesium reduces myocardial infarct size via enhancement of adenosine mechanism in rabbits.
OBJECTIVE
Clinical impact of magnesium (Mg) therapy remains controversial in acute myocardial infarction. We investigated the infarct size limiting effects of Mg and its mechanism in rabbits.


METHODS
Anesthetized rabbits underwent 30 min coronary occlusion and 3 h reperfusion in ten groups: (1) Control, (2) Low Mg, (3) Mg, (4) High Mg, (5) calcium (Ca), (6) Mg+Ca, (7) 8-phenyltheophylline (8PT), an adenosine receptor blockade, (8) 8PT+Mg, (9) alpha, beta-methylene-adenosine diphosphate (AOPCP), a selective inhibitor of ecto-5'-nucleotidase, and (10) AOPCP+Mg groups. Infract size (IS) to area at risk (AR) was measured by triphenyltetrazorium chloride method.


RESULTS
The IS/AR ratio was significantly smaller in Mg, 27+/-3% (P<0.05) and High Mg, 24+/-2% (P<0.05) compared to Control, 50+/-3% and Low Mg, 42+/-4%. The IS limiting effects of Mg were abolished in 8PT+Mg, AOPCP+Mg and Mg+Ca. The IS/AR ratio correlated with neither rate-pressure products nor incidence of arrhythmia.


CONCLUSIONS
Magnesium administration has an infarct size limiting effect independent of its effects on myocardial oxygen consumption and incidence of arrhythmia in rabbits. The infarct size limiting effect of magnesium is attributable, at least in part, to augmentation of adenosine mechanism.
Matsusaka
Tomoyuki
T
First Department of Internal Medicine, Asahikawa Medical College, 2-1-1-1 Midorigaokahigashi, Asahikawa, Hokkaido, Japan.
Hasebe
Naoyuki
N
Jin
Yin Tie
YT
Kawabe
Junichi
J
Kikuchi
Kenjiro
K
D015720:5'-Nucleotidase / Q000037:antagonists & inhibitors; D000241:Adenosine / Q000378:metabolism*; D000244:Adenosine Diphosphate / Q000031:analogs & derivatives* / Q000494:pharmacology; D000704:Analysis of Variance; D000818:Animals; D002118:Calcium / Q000627:therapeutic use; D004357:Drug Synergism; D004791:Enzyme Inhibitors / Q000627:therapeutic use; D008274:Magnesium / Q000627:therapeutic use*; D008297:Male; D023421:Models, Animal; D009203:Myocardial Infarction / Q000378:metabolism* / Q000473:pathology*; D009206:Myocardium / Q000473:pathology*; D058915:Purinergic P1 Receptor Antagonists; D011817:Rabbits; D013806:Theophylline / Q000031:analogs & derivatives* / Q000627:therapeutic use
D004791:Enzyme Inhibitors; D058915:Purinergic P1 Receptor Antagonists; C523965:alpha,beta-methyleneadenosine 5'-diphosphate; D000244:Adenosine Diphosphate; D013806:Theophylline; C028322:8-phenyltheophylline; D015720:5'-Nucleotidase; D008274:Magnesium; D000241:Adenosine; D002118:Calcium