Sodium arsenite augments sensitivity of Echinococcus granulosus protoscoleces to albendazole. 
This study aimed to observe the effects of sodium arsenite (NaAsO2) on apoptosis of Echinococcus granulosus protoscoleces induced by albendazole (ABZ), and to explore the potential mechanism of NaAsO2.  According to the following final concentrations, the experimental groups were divided into 10 μM NaAsO2, 20 μM NaAsO2, 80 μM ABZ, 10 μM NaAsO2+80 μM ABZ, and 20 μM NaAsO2+80 μM ABZ.  Viability was detected with 0.1% eosin staining.  The ultrastructural alterations were visualized by scanning electron microscopy.  Caspase-3 activity was assessed with colorimetric assay.  Meanwhile, ELISA or WST were applied to detect the activities of antioxidases in NaAsO2 treatment groups.  The maximum protoscolicidal effect was seen with the combination 20 μM NaAsO2+80 μM ABZ.  The ultrastructural damage detected after NaAsO2+ABZ incubation were greater than those caused by ABZ alone and its primary damage site was the tegument of the parasite.  The caspase-3 activity was clearly higher in protoscoleces treated with the combination of NaAsO2+ABZ than when drugs were used separately.  The activities of NQO-1, HO-1, GST, and SOD were significantly lower in protoscoleces incubated with NaAsO2 than the untreated controls (P < 0.05).  According to our results, ABZ could induce protoscoleces apoptosis, and NaAsO2 could significantly augment sensitivity of protoscoleces to ABZ.