EFFECT OF TEMPERATURE AND MONENSIN ON THE LEVEL OF INTRACELLULAR SODIUM AND pH IN PERFUSED RIF-1 CULTURE CELLS (A.M. Babsky, M.Yu. Klevets, N. Bansal)

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Journal archive > 2007 > N 4 July-August

EFFECT OF TEMPERATURE AND MONENSIN ON THE LEVEL OF INTRACELLULAR

SODIUM AND pH IN PERFUSED RIF-1 CULTURE CELLS

A. M. Babsky^1,2, M. Yu. Klevets², N. Bansal¹

¹Indiana University, Indianapolis, USA;

²Ivan Franko National University, Lviv, Ukraine;

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The direct measurement of temperature in subcutaneously (sc) implanted tumors shows that the actual tumor temperature is by 3–4 °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 °C. The temperature increase during the perfusion of radiation-induced fibrosarcoma (RIF-1) cells from 33 to 37 °C caused a reversible increase in intracellular ²³Na ([Na⁺]_i) NMR signal intensity by 50–60%. This heating significantly decreased the intracellular pH (pH_i) in 5 min, but it returned back to the baseline level during the heating period. The ?ATP/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 pHi and ?ATP/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.

Key words: RIF-1, temperature, sodium, monensin, pH, NMR.

The original article in Ukrainian is available for download in PDF format.