[Hydralazine-induced enhancement of hyperthermia treatment in vivo].

Hydralazine (Hyd) is a vaso-active drug that significantly affects the nature of blood flow in tumors. As a result, Hyd reduces blood flow and oxygen tension in tumors, causing an increase in the toxic effect of hyperthermia treatment. We investigated enhancement of the anti-tumor effect of hyperthermia by Hyd on SCC-VII tumors in C3H mice. Hyd was administered by intraperitoneal injection, and tumors were heated by water bath. We measured the tumor temperature in animals receiving Hyd by thermocouple. We found no significant change in tumor temperature with Hyd treatment. The effect of Hyd (2.5 mg/kg, 5.0 mg/kg, 7.5 mg/kg) on tumors was evaluated in terms of a growth delay value at which tumor volume reached four-fold. The growth delay values obtained were 6.25 +/- 0.82, 7.14 +/- 0.90, 8.50 +/- 0.98, 9.72 +/- 0.92, and 9.84 +/- 1.3 days for: hyperthermia alone, Hyd of 1.0 mg/kg, 2.5 mg/kg, 5.0 mg/kg, respectively. This effect was independent of the time course of administration of Hyd. These results indicate that Hyd can increase the therapeutic efficacy of hyperthermia treatment. Changes in the microenvironment, such as low pH and tumor hypoxia, induced by arterial embolization may have increased the sensitivity of tumors to heat.