On the mechanism of a 60-Hz electric field induced growth reduction of mammalian cells in vitro.

Data on 60-Hz electric field (EF) induced reduction in growth rate of plant roots have strongly supported the hypothesis that the effect is related to an EF-induced transmembrane potential (Vim). An investigation was undertaken to determine if this hypothesis is also applicable to 60-Hz EF-induced reductions in growth rate of mammalian cells in vitro. Human lymphoblastic (RPMI 1788) and human carcinoma (HeLa) cells were selected for study, the former having a relatively small diameter (11.2 microns), and the latter having a relatively large diameter (15.4 microns). The 60-Hz EFs ranged from 430-1200 V/m in the culture medium. The growth rate of RPMI 1788 cells after 4-days was depressed by about 42% at a 60-Hz EF of 1000-1200 V/m with a response threshold occurring at 950 V/m; the Vim at the response threshold was 8 mV. There was no 60-Hz EF-induced effect on HeLa cell growth rate of a Vim of 8 mV (60-Hz EF = 700 V/m); a statistically significant effect was achieved at Vim of 11 mV (950 V/m). The data support the hypothesis that above a threshold 60-Hz EF, Vim acts as the initial signal leading to growth rate reductions.