THE ROLE OF ACTIVE OXYGEN SPECIES AND LIPID-PEROXIDATION IN THE ANTITUMOR EFFECT OF HYPERTHERMIA

The role of active oxygen species and lipid peroxidation in the antitu mor effect of hyperthermia was studied in an experimental rabbit model . VX2 tumors were transplanted into rabbit hind legs, and the effect o f hyperthermia on tumor growth was measured at 7 and 14 days after hea ting. As an index of lipid peroxidation, thiobarbituric acid-reactive substances in the tumor tissue were measured prior to hyperthermia and 3, 6, 12, and 24 h after hyperthermia. Tumor growth in rabbits treate d with hyperthermia was significantly reduced, and thiobarbituric acid -reactive substances in the tumor tissue treated with hyperthermia wer e significantly increased until 6 h after hyperthermia. In addition, a lpha-tocopherol in the tumor tissue was significantly decreased after hyperthermia. The antitumor effect of hyperthermia and the increase of thiobarbituric acid-reactive substances in the tumor tissue treated w ith hyperthermia were significantly inhibited by the administration of superoxide dismutase and catalase or dimethyl sulfoxide. These result s suggest that lipid peroxidation mediated by active oxygen species pl ays an important role in the antitumor effect of hyperthermia.