The effect of primaquine on the enzymatic antioxidant defence mechanisms of erythrocytes were determined by measuring the activities of the below enzymes, before and after 30 minutes of incubation of hemolyzates with 1 mM primaquine at 37°C. Among the enzymes studied glucose-6- phosphate dehydrogenase seemed the most sensitive enzyme; 57 % and 78 % inhibition at zero (due to the binding of primaquine to NADP binding site) and 30 minutes of incubation (due to the reactive oxygen species), respectively. Catalase, superoxide dismutase, and glutathione-S-transferase were less sensitive to primaquine-derived reactive oxygen species: 33, 11, and 0 % inhibition at the time zero and 39, 27, and 4 %, at the end of 30 minutes of incubation. Glutathione reductase and glutathione peroxidase were resistant to primaquine-derived reactive oxygen species. The Primaquine-mediated toxicity, in vivo, due to the rimaquine-NAD(P)H or/and primaquine-glucose-6-phosphate dehydroge-nase interaction, will cause damage and the degree of the damage will depend on: i. concentration of the drug, PQ; ii. incubation period and; iii. the type of the system affected. The study of the interaction of reactive oxygen species with these enzymes, will help to better understand the role of protective enzyme systems in erythrocytes to oxidative stress.

The effect of primaquine on the enzymatic antioxidant defence mechanisms of erythrocytes were determined by measuring the activities of the below enzymes, before and after 30 minutes of incubation of hemolyzates with 1 mM primaquine at 37°C. Among the enzymes studied glucose-6- phosphate dehydrogenase seemed the most sensitive enzyme; 57 % and 78 % inhibition at zero (due to the binding of primaquine to NADP binding site) and 30 minutes of incubation (due to the reactive oxygen species), respectively. Catalase, superoxide dismutase, and glutathione-S-transferase were less sensitive to primaquine-derived reactive oxygen species: 33, 11, and 0 % inhibition at the time zero and 39, 27, and 4 %, at the end of 30 minutes of incubation. Glutathione reductase and glutathione peroxidase were resistant to primaquine-derived reactive oxygen species. The Primaquine-mediated toxicity, in vivo, due to the rimaquine-NAD(P)H or/and primaquine-glucose-6-phosphate dehydroge-nase interaction, will cause damage and the degree of the damage will depend on: i. concentration of the drug, PQ; ii. incubation period and; iii. the type of the system affected. The study of the interaction of reactive oxygen species with these enzymes, will help to better understand the role of protective enzyme systems in erythrocytes to oxidative stress.