Evidence for growth inhibition by platinum electrodes at low current levels.

Platinum is considered to be a noble metal and is often used for electrodes in biological investigations. However, platinum electrodes can form inhibitory compounds, as pointed out by Rosenberg et al. 1965. The aim of this study was to investigate whether platinum electrodes are inert in the extremely low frequency (ELF) range of currents. Human bone marrow cells cultured in agar were used as target cells and were grown under various electrical conditions. A 50% reduction in growth compared with controls was obtained by average currents of 2300 microA at 8 Hz and 110 microA at 80 Hz, the current being derived from a square bipolar voltage waveform. D.c. currents were also inhibitory, with a value of 50% at the 1.4 microA level. The cells were probably not affected directly by the current, since inhibitory properties could be stored in agar and saline and because titanium electrodes at equal current levels did not produce the same effect.