Effect of the herbicide 4-CPA on human erythrocyte antioxidant enzymes<i>in vitro</i>

To investigate the possible role of oxygen free radicals and oxidant stress in the toxic effects of phenoxyherbicides, we studied the in vitro effect of 4-chlorophenoxyacetic acid (4-CPA) on various human erythrocyte antioxidant enzymes, namely glucose-6-phosphate dehydrogenase, catalase, selenium-dependent glutathione peroxidase, glutathione reductase and Cu/Zn-superoxide dismutase. 4- CPA added in a dose of 1 ppm to human erythrocytes for 1 h caused a significant reduction in glucose-6- phosphate dehydrogenase (P <0.001) and catalase (P <0.001) activities, but did not significantly affect the activities of other enzymes. Such selective inactivation of specific erythrocyte antioxidant enzymes may play a role in the toxic effects of phenoxyherbicides.