Relationship between vascular thermotolerance and intratumor pH.

Abstract

The changes in blood flow, intratumor pH, and clonogenicity of tumor cells after one and two heatings were studied in SCK tumors of A/J mice. When SCK tumors were heated at 42.5 degrees C for 1 hr, vascular thermotolerance promptly developed and peaked at 18 hr post-heating. The intratumor pH was 7.05 +/- 0.14 (mean +/- S.D.) in control SCK tumors of A/J mice, with a significant decrease (p less than or equal to 0.001) to 6.86 +/- 0.08 and 6.70 +/- 0.08 when heated for 1 hr at 43.5 degrees C and 44.5 degrees C, respectively. However, when the vascular thermotolerance was at its peak, heating at the same doses caused little change in the intratumor pH. When SCK tumors were heated for the first time at 44.5 degrees C for 1 hr and left in situ, the number of clonogenic cells significantly declined. Such a secondary cell death could be attributed to the deterioration of the intratumor environment ensuing from the vascular damage. When the tumor vessels were thermotolerant, however, virtually no secondary cell death occurred after heating.