Studies on ammonia-metabolizing enzymes during Plasmodium yoelii infection and pyrimethamine treatment in mice.

Blood ammonia content and enzymes involved in ammonia metabolism, namely glutamine synthetase (GS), glutamate dehydrogenase (GDH), monoamine oxidase (MAO), alanine amino-transferase (ALT) and aspartate aminotransferase (AST), were studied in Plasmodium yoelii-infected drug-treated mice tissues. The ammonia content in blood increased with the rise of parasitaemia. Hepatic GS, GDH and MAO showed a marked decrease in enzyme activity during parasitic infection. In contrast, cerebral GS and MAO showed a significant increase during infection. However, the parallel measurement of renal enzymes did not show any noticeable alterations except for ALT and AST. Oral pyrimethamine treatment (10 mg/kg for 4 days) in infected mice (5-10%) returned the altered levels of the above enzymes to almost normal 1 week after the cessation of drug treatment.