DNA-SYNTHESIS AND CELL-PROLIFERATION IN C-6 GLIOMA AND PRIMARY GLIAL-CELLS EXPOSED TO A 836.55 MHZ MODULATED RADIOFREQUENCY FIELD

We have tested the hypothesis that modulated radiofrequency (RF) field s may act as a tumor-promoting agent by altering DNA synthesis, leadin g to increased cell proliferation. In vitro tissue cultures of transfo rmed and normal rat glial cells were exposed to an 836.55 MHz, packet- modulated RF field at three power densities: 0.09, 0.9, and 9 mW/cm(2) , resulting in specific absorption rates (SARs) ranging from 0.15 to 5 9 mu W/g. TEM-mode transmission-line cells were powered by a prototype time-domain multiple-access (TDMA) transmitter that conforms to the N orth American digital cellular telephone standard. One sham and one en ergized TEM cell were placed in standard incubators maintained at 37 d egrees C and 5% CO2. DNA synthesis experiments at 0.59-59 mu W/g SAR w ere performed on log-phase and serum-starved semiquiescent cultures af ter 24 h exposure. Cell growth at 0.15-15 mu W/g SAR was determined by cell counts of log-phase cultures on days 0, 1, 5, 7, 9, 12, and 14 o f a 2 week protocol. Results from the DNA synthesis assays differed fa r the two cell types. Sham-exposed and RF-exposed cultures of primary rat glial cells showed no significant differences for either log-phase or serum-starved condition. Cs glioma cells exposed to RF at 5.9 mu W /g SAR (0.9 mW/cm(2)) exhibited small (20-40%) significant increases i n 38% of [H-3]thymidine incorporation experiments. Growth curves of sh am and RF-exposed cultures showed no differences in either normal or t ransformed glial cells at any of the power densities tested. Cell doub ling times of C-6 glioma cells [sham (21.9 +/- 1.4 h) vs. field (22.7 +/- 3.2 h)] also demonstrated no significant differences that could be attributed to altered DNA synthesis rates. Under these conditions, th is modulated RF field did not increase cell proliferation of normal or transformed cultures of glial origin. (C) 1997 Wiley-Liss, Inc.