[Effect of temperature and monensin on the level of intracellular sodium and pH in perfused RIF-1 cultured cells].
The direct measurement of temperature in subcutaneously (sc) implanted tumors shows that the actual tumor temperature is by 3-4 degrees C lower than the normal body temperature. Thus, the temperatures usually used for tumor hyperthermia are in fact heating the sc-tumors from 33 to 37 degrees C. The temperature increase during the perfusion of radiation-induced fibrosarcoma (RIF-1) cells from 33 to 37 degrees C caused a reversible increase in intracellular 23Na ([Na+]i) NMR signal intensity by 50-60%. This heating significantly decreased the intracellular pH (pH) in 5 min, but it returned back to the baseline level during the heating period. The 3ATP/P(i) remained generally unchanged throughout the experiment. Monensin, an antitumoral drug and Na+ ionophor, increased [Na+]i by 20% during cell superfusion without heating. When combined, monensin did not increase the heating effect on [Na+]i. However, when monensin was added to the superfusion media, the [Na+]i level did not return to baseline during post-heating recovery, but instead started to increase again. Monensin did not significantly change pH(i) and betaATP/P(i). Our data and the literature show that monensin can accelerate the processes leading to the collapse of the transmembrane Na+ gradient and thus can increase the thermo-sensitivity of tumor cells.
Babs'kyĭ
A M
AM
Klevets'
M Iu
MIu
Bansal
N
N
D000818:Animals; D000970:Antineoplastic Agents / Q000494:pharmacology*; D045744:Cell Line, Tumor; D005354:Fibrosarcoma / Q000378:metabolism; D006358:Hot Temperature; D006863:Hydrogen-Ion Concentration; D009682:Magnetic Resonance Spectroscopy; D008985:Monensin / Q000494:pharmacology*; D010477:Perfusion; D012964:Sodium / Q000378:metabolism*
D000970:Antineoplastic Agents; D008985:Monensin; D012964:Sodium