The effect of hyperthermia on vascular function, pH, and cell survival.

Abstract

Blood flow in rat skin and muscle increased 3- to 4-fold during heating at 43.degree. C for 1 h; while that in [rat] Walker tumor cells did not change significantly; blood flow in the tumors decreased a few hours after heating at 45.degree. C. The temperature of Walker tumors was significantly higher than in the muscle during heating, probably due to inefficient heat dissipation caused by the sluggish blood flow. Severe vascular occlusion occurred in [mammary adenocarcinoma] SCK tumor cells in mice after heating at 41.5-45.0.degree. C. Upon heating, the pH in the tumors signifiantly decreased while that in the muscle increased. The clonogenic cell number continuously decreased when SCK tumors were left in situ after hyperthermia for cancer therapy. The vascular occlusion and increase in acidity may account for the progressive death of tumor cells after heating.