RESUMO
The effects of Na_2MoO_4 on experimental ventricular arrhythmias and isolated guinea pig atria are reported. Iv Na_2MoO_4, 8 mg/kg was found to increase the tolerant dose of ouabain to produce ventricular permature beats, ventricular tachycardia and ventricular fibrillation in guinea pigs. Na_2MoO_4 significantly counteracted the ventricular arrhythmias induced by BaCl_2 and aconitine in rats. Na_2MoO_4 10 ?g/10 g ip decreased the incidence of ventricular fibrillation by chloroform in mice, Na_2MoO_4 10 mg/kg did not produce antagonistic effect on the arrhythmias induced by chloroform-adrenaline in rabbits. Na_2MoO_4 0.1 mmol/L inhibited contractility of isolated guinea pig atria, prolonged the functional refractory period and makedly inhibited the frequency-dependent positive staircase phenomenon and the post-rest potentiation.