QUANTITATIVE STUDY OF CALCIUM-UPTAKE BY TUMORIGENIC BONE (TE-85) AND NEUROBLASTOMA X GLIOMA (NG108-15) CELLS EXPOSED TO EXTREMELY-LOW-FREQUENCY (ELF) ELECTRIC-FIELDS

To verify the effect of cell culture state on frequency dependent incr ease in proliferation as well as Ca2+ flux across the plasma membrane, tumorigenic bone (TE-85) and neuroblastoma x glioma (NG108-15) cells cultured in the presence of fetal bovine serum (FBS) were exposed to c apacitively coupled electric (CCEF) fields in the extremely low freque ncy (ELF) range of 10 to 18 Hz. [H-3]Thymidine incorporation and Ca-45 (2+) uptake were used as endpoints, TE-85 cells cultured in the presen ce of 10% FBS did not exhibit a frequency dependent increase in prolif eration in contrast to previous studies under growth arrested culture conditions, in which the cells were deprived of FBS, However, both TE- 85 and NG108-15 cells had an increase in Ca-45(2+) uptake in response to a 16 Hz 18.3 mV/cm CCEF, Fura-2 digital imaging microscopy was used to verify addition of 0.5 mM La3+ and 0.5 mM ionomycin as negative an d positive controls, respectively. Imaging microscopy data was combine d with Ca-45(2+) incorporation results to quantify free intracellular calcium ([Ca2+](i)) increase in response to CCEF exposure, TE-85 [Ca2](i) increased from 140 to 189-210 nM where as NG108-15 [Ca2+](i) incr eased from 67 to 189-210 nM, These results suggested that serum depriv ation may be a requirement for a frequency dependent increase in proli feration in TE-85 cells but is not necessary for the electric field in duced increase in Ca-45(2+) uptake in both TE-85 and NG108 cells, The present study also represents the first demonstration of increased Ca- 45(2+) uptake by neuroblastoma and/or glioma cells in response to an e lectric field exposure. (C) 1997 Federation of European Biochemical So cieties.