AIM To investigate the effect of methyl pentyl 1,4 dihydro 2,6 dimethyl 4 (3 nitrophenyl) 3,5 pyridinedicarboxylate
(MN9202),a dihydropyridine
calcium antagonist, on cardiac indexes,
ultrastructure, superoxide dismatase (SOD),glutathione peroxidase (GSH PX) activity and malondialdehyde (MDA) concentration in cardiac hypertrophy induced by L thyroxine (L Thy) in rats. METHODS cardiac hypertophic model of rats was induced by a continued administration of L Thy 0.5 mg·kg -1 ip once daily for 12 d. Three doses (0.4, 2, 10 mg·kg -1 ) of MN9202 or captopril (25 mg·kg -1 , positive group), vehicle (model group or control group) were injected by ip before 8 h L Thy injection; cardiac indexes were examined; the change of myocardial ultrastructure were observed with electron microscope; the activity of SOD, GSH PX and concentration of MDA were measured by colorimetric analysis. RESULTS by a continued ip L Thy for 12 d, MN9202 could obviously reduce the cardiac indexes, improve the development of ultrastructural pathological change at myocardium and significently increased the SOD,GSH PX activity and reduce the production of MDA in rats, especially in middle dose and high dose ( P <0.05, P <0.01). CONCLUSION MN9202 can inhibit cardiac hypertrophy induced by L Thy and protect cardiac tissue from injury, which may be related to blocking intracellular Ca 2+ influx, reduceing calcium accumulation and increasing the activity of clearence enzyme of free radical and inhibiting lipid peroxidation