The effects of tetrandrine on the contractile function and microvascular permeability in the stunned myocardium of rats

The effects of tetrandrine (Tet) on the contractile function and microvascular permeability in stunned rat myocardium in vivo were studied. Stunned myocardium was induced by 15 (MS15 group) or 20 (MS20 group) min of myocardial ischemia plus 60 min of reperfusion, The following was shown. (1) FITC-BSA concentration was 166.0+/-7.9 mu g/g myocardium in the control group.:The concentrations in ischemic myocardium increased by 35.4 and 45.6% in MS15 and MS20 groups, respectively (p<0.05). (2) Administration of Tet (64.2 and 96.3 mu mol/kg, I.P.) 20 min before ischemia not only ameliorated the contractile function, but also reduced the FITC-BSA concentrations in ischemic myocardium, At 60 min after reperfusion, the contractile function parameters in Tet-treated groups were significantly superior to those in corresponding stunning groups. FITC-BSA concentrations in Tet-treated groups were lower than those in stunning groups. Then, there was already no significant difference in FITC-BSA concentrations between Tet-treated groups and the control group. The FITC-BSA concentrations at the end of experiments:were correlated negatively with dp/dt(max) (r = -0.83, p<0.01). (3) Tet inhibited KCl-induced calcium influx in isolated cardiomyocytes. The results suggest that Tet given before ischemia may be involved in the reduction of microvascular permeability in stunned myocardium, which might be associated with its calcium channel blocking effect.