Ferric Nitrilotriacetate (Fe-NTA) Is a Potent Hepatic Tumor Promoter and Acts Through the Generation of Oxidative Stress

Abstract

Fe-NTA is a known renal carcinogen. However, little is known about its carcinogenic potential in liver. In this study we for the first time show that Fe-NTA is a potent hepatic tumor promoter. Fe-NTA administration induced dose dependently the hepatic ornithine decarboxylase (ODC) activity several folds as compared to its activity in the saline-treated rats. Similarly, hepatic DNA synthesis which is measured as [3H]thymidine incorporation in DNA is also increased following Fe-NTA treatment. The effects of Fe-NTA were similar to other tumor promoters not only with respect to inducing ODC activity and [3H]thymidine incorporation in DNA but also in depleting antioxidant armory of the tissue. Fe-NTA depleted levels of glutathione to about 35% of the saline-treated control and activities of antioxidant enzymes catalase, glutathione peroxidase, glutathione reductase and glucose 6-phosphate dehydrogenase decreased significantly (45-55% of saline-treated control). Concomitant with the depletion in antioxidant armory, Fe-NTA augmented hepatic microsomal lipid peroxidation more than three folds. The pretreatment of rats with antioxidants BHA or BHT diminished the observed effects of Fe-NTA. Our data indicate that Fe-NTA is a potent hepatic tumor promoter and acts through a mechanism involving oxidative stress.