[Effect of hydralazine on the blood flow of normal and tumor tissues in hyperthermia]

We examined changes in blood flow in normal muscle and SCC-VII tumors of C 3 H/He mice following hyperthermia (HT) combined with the vasodilator hydralazine (Hyd) and compared them with similar changes after Hyd treatment or HT alone. Blood flow was measured by the Laser Doppler method, and oxygen tension was evaluated by polarography. The mean blood flow for the tumors in the Hyd group decreased. After HT treatment, it decreased to a low level. The largest decrease in tumor blood flow was observed after HT combined with Hyd administration. In normal muscle, no decrease in blood flow was induced by HT, Hyd or their combination. The magnitude of action of Hyd on the heat-induced changes in tumor blood flow and on damage to tumor vessels is considered to depend on the initial perfusion level. Therefore, we tried to clarify how this parameter was correlated with Hyd and/or HT-induced changes. In the HT and combined groups, the higher the temperature, the more significant the decrease in blood flow. In conclusion, these results suggest that the decrease in blood flow inside the tumor caused by Hyd plays an important role in enhancement of the hyperthermic anti-tumor effect.