Enhancement of antitumor effect of hyperthermia with glucose administration in murine mammary carcinoma

Antitumor effects of hyperthermia are enhanced by lowering the pH in the tu mor tissue with administration of glucose. This decreased pH in the tumor t issue with glucose administration was determined using mouse experimental t umors. P-31-MRS microelectrodes were used for the measurement of pH. By usi ng these two measurement methods, time course change in the tumor tissue wa s determined in the controls and the groups treated with 6 g/kg of intraper itoneal glucose. The determination of pH with P-31-MRS was calculated from the; chemical shift of the peak of creatine phosphate (Pcr) and that of ino rganic phosphate (Pi). Following glucose administration, the tumor tissue s howed a decrease of 0.3 pH units with the microelectrode method, but did no t show any significant decrease in pH with the MRS determination. This find ing suggested that P-31-MRS showed intracellular pH (pHi) due to the locali zation of Pi and that the microelectrode indicated interstitial or extracel lular pH (pHe). The ATP/Pi ratio obtained in tumor tissue 24 h after heat t reatment (with, without glucose) was correlated with tumor inhibition.