Determination of extracellular pH and tissue temperature in transplantable rat tumors by use of inductive loop telemetry.

Radiotelemetry was used to determine changes in extracellular pH and tissue temperature during tumor development in rats of an inbred WAB substrain. A progressive decrease in the pH of the tumor tissue compared with the pH level in control tissue was observed, so that by 4 days after tumor implantation the tumor tissue was about 0.4 pH units lower than control values. Thereafter, tumor pH rose progressively to reach a value comparable with control levels at 8 days, when the experiment was terminated. No significant difference was detected between the temperature in the tumor tissue and the temperature in the control tissue. Therefore, the observed changes in pH appeared to be independent of temperature. Studies on the rate of tumor cell proliferation during the experiments demonstrated a significant inverse relationship between tumor cell mitotic rate and pH, with the highest rates of cell proliferation occurring at the time of lowest pH values.