title en

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. Babsky1,2, M. Yu. Klevets2, N. Bansal1

1Indiana University, Indianapolis, USA;
2Ivan Franko National University, Lviv, Ukraine;
e-mail: This email address is being protected from spambots. You need JavaScript enabled to view it.

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 (pHi) in 5 min, but it returned back to the baseline level during the heating period. The ?ATP/Pi 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/Pi. 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.

© The Ukrainian Biochemical Journal