Studies on Nuclear Division of a Malarial Parasite under Pyrimethamine Treatment

Pyrimethamine is an antimalarial drug which possesses schizonticidal activity in both tissue and blood phases. Though pyrimethamine is known to inhibit folic acid metabolism of malarial parasites by binding with folio acid reductase (6), the cytological effect on the parasites is not completely understood. To our knowledge, there has been no study until now on the morphological effects of pyrimethamine on malarial parasites. However, Thurston (11), using light microscopy, reported the effects of a similar antimalarial drug, proguanil, on the nuclear division of the erythrocytic stages of Plasmodium berghei. Since proguanil and pyrimethamine exert qualitatively similar effects on malarial parasites (8), pyrimethamine is also thought to act against nuclear division of malarial parasites. In this investigation, we have studied with electron microscopy the morphological effects of pyrimethamine on the erythrocytic stages of a malarial parasite, Plasmodium gallinaceum. It is hoped that pyrimethamine may be used for the study of nuclear division in malarial parasites, which is still poorly understood.