Effect of pyronaridine on ultrastructure of erythrocytic forms of Plasmodium berghei in mice

About 0.25-0.5 h after a single dose (6 mg/kg,ED50) of pyronaridine ig to the mice infected with Plasmodium berghei,swelling of pellicular complexes,formation of multilamellate whorls in the complexes,and fusion, enlargement and pigment aggregation of food vacuoles in the trophozoites of the parasites were observed, then followed by changes of mitochondria, endoplasmic reticulum and nuclear membrane,deformities of ribosomes and nuclear chromatin. Ultrastructural disintegrations were noted in a few trophozoites after 4 h, while most of those lesions occurred in 16 h.The ultrastructural changes in the schizonts were similar to those in th trophozonites after 1-2 h and no more schizonts were found after 16 h. The results suggested that pyronaridine exerted its potent and rapid lethal action on the erythrocytic forms of Plasmodium berghei by interfering in physiological function of the pellicular complexes and food vacuoles.