Radio-frequency rectification in electrogenic and nonelectrogenic cells ofChara andNitella

Abstract

Electrogenic cells ofChara braunii andNitella flexilis were placed in a pulse-modulated radio-frequency electric field of up to 6000 V/m. Their vacuolar resting potentials were found to experience submillivoltdepolarizing offsets (typically 140 μV at 250 kHz) which were relatively indepencent of temperature, increased linearly with resting potential from a zero near −210mV, and had a cutoff (putatively due to ion transit times) near 5 MHz. By contrast, nonelectrogenic cells experiencedhyperpolarizing offsets (typically 1100 μV at 250 kHz) which increased in magnitude with increasing temperature, were independent of resting potential, and had a transit time cutoff near 10 MHz. The ionic mobilities inferred from these cutoff frequencies are somewhat higher than would be expected for active transport and presumably reflect passive conductance mechanisms which therefore must be presumed different for the electrogenic and nonelectrogenic states.