The effects of radiofrequency fields on cell proliferation are non-thermal

The number of reports on the effects induced by radiofrequency (RF) electro magnetic fields and microwave (MW) radiation in various cellular systems is still increasing. Until now no satisfactory mechanism has been proposed to explain the biological effects of these fields. One of the current theorie s is that heat generation by RF/MW is the cause, in spite of the fact that a great number of studies under isothermal conditions have reported signifi cant cellular changes after exposure to RF/MW. Therefore, this study was un dertaken to investigate which effect MW radiation from these fields in comb ination with a significant change of temperature could have on cell prolife ration. The experiments were performed on the same cell line, and with the same exposure system as in a previous work [S. Kwee, P, Raskmark, Changes i n cell proliferation due to environmental non-ionizing radiation: 2. Microw ave radiation, Bioelectrochem. Bioenerg., 44 (1998), pp. 251-255]. The fiel d was generated by signal simulation of the Global System for Mobile commun ications (GSM) of 960 MHz. Cell cultures, growing in microtiter plates, wer e exposed in a specially constructed chamber, a Transverse Electromagnetic (TEM) cell. The Specific Absorption Rate (SAR) value for each cell well was calculated for this exposure system. However, in this study the cells were exposed to the field at a higher or lower temperature than the temperature in the field-free incubator i.e., the temperature in the TEM cell was eith er 39 or 35 +/- 0.1 degrees C. The corresponding sham experiments were perf ormed under exactly the same experimental conditions. The results showed th at there was a significant change in cell proliferation in the exposed cell s in comparison to the non-exposed (control) cells at both temperatures. On the other hand, no significant change in proliferation rate was found in t he sham-exposed cells at both temperatures. This shows that biological effe cts due to RF/MW cannot be attributed only to a change of temperature. Sinc e the RF/MW induced changes were of the same order of magnitude at both tem peratures and also comparable to our previous results under isothermal cond itions at 37 degrees C, cellular stress caused by electromagnetic fields co uld initiate the changes in cell cycle reaction rates. It is widely accepte d that certain classes of heat-shock proteins are involved in these stress reactions. (C) 1999 Elsevier Science S.A. All rights reserved.