Hyperthermic "dose" dependent changes in intralesional pH.

Abstract

Following hyperthermia a dramatic drop in intra-lesional pH has occurred in a variety of experimental tumor systems. To date, no direct observations have been made that document the time course of such changes or the recovery from such changes over prolonged periods of time. These experiments were designed to measure intralesional pH as a function of time following "doses" of hyperthermia related to specific biological end points. All studies were conducted in the C3H-mammary carcinoma tumor model system. Intralesional temperature was continuously monitored throughout treatment and post treatment pH was measured with microelectrodes at several specific time points ranging from 4 hrs to 7 days. The pretreatment control value of mean pH was 6.73. At the TCD90 "dose" level the mean value of pH dropped to a level of 6.22 +/- .095 while following the TCD10 "dose" the value obtained was 6.55 +/- .148. Recovery of the pH to higher values followed similar time courses returning to maximum values approximately 3 days post treatment. The recovery, plateau levels of pH were however, separated by approximately .3 pH units with the higher "dose" curve always at lower values than that achieved following the lower "dose".