Objective: To investigate the changes of
myocardial contractile function during
myocardial stunning in calcium overload rats
and the protective effects of tetrandrine. Methods: Forty six rats were randomized into control, myocardial ischemia,
myocardial stunning, low and high dose of tetrandrine groups. Another 10 rats were used to identify the calcium overload. vitamin D 3 (0.3 million Unit/kg) and nicotinic acid were administered. After 16 d when calcium overload occured, left anterior descending artery was ligated. Twenty minutes of myocardial ischemia followed by 60 min of reperfusion was induced. The contractile function parameters were determined dynamically. At the end of experiment, myocardial cytosolic
i was determined in various groups. In tetrandrine groups, tetrandrine (62.2 or 93.6 μmol/kg ) was administered by gastrogavage daily.After 16 d, the rats undergone the experiments mentioned above. Results: Sixteen days after vitamin D 3, nicotinic acid were given, i increased by 2.6 folds (146.8±10.8) vs (368.5±22.6) nmol/L, ( P <0.01). Whereas, i in tetrandrine groups were (210.8±16.4) and (198.6±15.3) nmol/L, which were significantly lower than that of calcium overload group. Twenty minutes of myocardial ischemia resulted in the decrease of dp/dtmax and Vmax in all groups with the most significant in stunning and calcium overload groups. The contractile function restored gradually after reperfusion. At all time points, dp/dtmax and Vmax in both tetrandrine groups were higher than those in both stunning and calcium overload groups. And effect with higher dose of tetrandrine were more significant than in low dose of tetrandrine. After 60 min of reperfusion, dp/dtmax in stunning, calcium overload, low and high dose of tetrandrine groups were 49.7%, 51.5%, 71.0% and 83.4% of that in control, respectively, and Vmax were 55.0%, 49.8%, 73.9% and 77.5% of that in control, respectively. Conclusion: The myocardial contractile function in vitamin D 3 induced calcium overload group is impaired. On basis of myocardiocyte calcium overload, transient ischemia leads to myocardial stunning. At the stage of ischemia, the impaired degree of myocardial contractile function is similar to that in stunning group, suggesting at this stage the effect of ischemia on myocardial function is greater than that of calcium overload. Tetrandrine chronically improves the myocardial function in Vitamin D 3 induced calcium overload rats. <