Objective    To investigate the protective effects of preconditioning with different fractions extracted from Panax japonicus C. A. Mey on acute myocardial ischemia in rats induced by ligating of the left anterior descending branch (LAD).      Methods    Fifty Wistar rats were evenly and randomly divided into a sham group

a model group and three treatment groups. The treatment groups were given different fractions extracted from Panax japonicus C. A. Mey

i.g.

an ethyl acetate fraction

an n-butyl alcohol fraction and a water fraction

separately. After preconditioning for 7 d

the acute myocardial ischemia models were constructed by  LAD. The electrocardiogram

infarct size and histomorphology were assessed 12 h after LAD. The activities of superoxide dismutase (SOD) and glutathione peroxidase (GSH-Px) as well as the levels of malondialdehyde (MDA) and cardiac troponin I (cTnI) in serum were also measured.     Results    The ethyl acetate

n-butyl alcohol and water fractions could significantly decrease the ST-segment elevation of electrocardiogram

and remarkably reduce the infarct size [(10.7±2.4)%

(9.8±2.6)% and (11.0±2.0)% vs (14.8±3.5)%

P0.05]. The myocardial inflammatory infiltration and lytic necrosis were alleviated due to the three fractions. Besides

the three fractions could significantly enhance the activities of SOD and GSH-Px

and reduce the levels of MDA and cTnI. The effect of the n-butyl alcohol fraction was significant as compared with the model group (P0.05)

and that of the water fraction was also significant as compared with the model group except for in the case of MDA (P0.05

P0.01).     Conclusion    The preconditioning with different fractions extracted from Panax japonicus C. A. Mey has significant protective effects on acute myocardial ischemia in rats. The n-butyl alcohol fraction has the most significant protective effect

followed by the water fraction.