Combining effects of epinephrine injected intratumorally and hyperthermia were studied in Lewis lung carcinoma growing in the hind legs of BDF1 mice. When 10% of epinephrine at the amount of 0.02 ml (0.14 mg/kg) was injected intraperitoneally or intratumorally, no growth inhibition was observed. However, when the same dose of epinephrine injected intratumorally was combined with 43.5°C of hyperthermia for 45 min, the effect on tumor growth delay was three times as the effect of hyperthermia alone. The sensitizing effect depended on temperature of hyperthermia and dose of epinephrine. The effect was significantly defferent between 1% epinephrine at 43.5°C for 30-45 min or 10% epinephrine at 40.5°C for 60 min and hyperthermia alone. Number of lung metastases was also inhibited by the combined therapy with high dose of epinephrine and 43.5°C of hyperthermia. Blood flows in the tumors were inhibited depending on the dose of epinephrine. The mechanisum of sensitizing effect was considered that reduced blood flow of the tumors by locally injected epinephrine induced the changes on tumor environment, perhaps decreased pH. Intratumoral injection of epinephrine seemed to be useful for clinical hyperthermia.
