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 microvascu lar permeability in stunned rat myocardium in vivo were studied. Stunned my ocardium was induced by 15 (MS15 group) or 20 (MS20 group) min of myocardia l ischemia plus 60 min of reperfusion, The following was shown. (1) FITC-BS A 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 cont ractile function, but also reduced the FITC-BSA concentrations in ischemic myocardium, At 60 min after reperfusion, the contractile function parameter s in Tet-treated groups were significantly superior to those in correspondi ng stunning groups. FITC-BSA concentrations in Tet-treated groups were lowe r than those in stunning groups. Then, there was already no significant dif ference in FITC-BSA concentrations between Tet-treated groups and the contr ol group. The FITC-BSA concentrations at the end of experiments:were correl ated 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 microvascula r permeability in stunned myocardium, which might be associated with its ca lcium channel blocking effect.