Comparison of the intensity of oxidative stress during chemotherapy alone and chemotherapy combined with antioxidant therapy in spontaneous mammary tumours in dogs.

As many anti-tumour drugs exert their cytotoxic effect via free radical-mediated mechanisms, the combined administration of antioxidants would alleviate side effects of the chemotherapy. The aim of this study was to evaluate the oxidant and antioxidant status of dogs with mammary adenocarcinomas after surgical removal of the tumours treated with chemotherapy (epirubicin and cyclophosphamide) alone (group I. n = 7) or coupled to antioxidant (vitamins E and Q supplementation (group II, n = 7) by monitoring the serum malondialdehyde (MDA), tocopherol and ascorbate concentrations and the catalase (CAT) activity in serum as well as the reduced glutathione (GSH) and superoxide dismutase activity in erythrocytes according to time. The co-administration of antioxidant vitamins with chemotherapeutic drugs markedly depressed the production of blood lipid peroxidation products (MDA). In parallel, the erythrocyte antioxidants were recruited (GSH concentrations declined and SOD activities increased) while serum antioxidants remained constant (vitamin Q or decreased (vitamin E) during the chemotherapy duration. Fifteen days after the end of treatment, the serum vitamin C concentrations become significantly higher in dogs supplemented with antioxidant vitamins whereas the serum vitamin E concentrations still remained depressed. These results suggest that the associated antioxidant treatment decreased the oxidative stress intensity by promoting the mobilisation of tissue antioxidant systems and exchanges with the blood store.