Highly specialized cells such as the cochlear outer hair cells responsible for hearing, exhibit cell membrane movement in response to a change in membrane voltage. In September 27 Nature, Ping-Cheng Zhang and colleagues from State University of New York at Buffalo show that less specialized cells, such as human embryonic kidney cells (HEK293), also react in less than a millisecond to changes in membrane voltage (Nature 2001, 413:428-432).

Zhang et al. used an atomic force microscope (AFM), to measure in real time the cellular movements of voltage-clamped HEK293 cells in different ionic-strength solutions. They found that in normal saline, depolarization caused an outward movement, while a low ionic strength caused an inward movement proportional to changes in membrane voltage (about 1 nm per 100 mV). In addition, salicylate — which inhibits cell motility by binding to the 'motor protein' prestin in cochlear cells — substantially reduces...

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