摘要：Even in nonexcitable cells, the membrane potential
V
m
is fundamental to cell function, with roles from ion channel regulation, development, to cancer metastasis.
V
m
arises from transmembrane ion concentration gradients; standard models assume homogeneous extracellular and intracellular ion concentrations, and that
V
m
only exists across the cell membrane and has no significance beyond it. Using red blood cells, we show that this is incorrect, or at least incomplete;
V
m
is detectable beyond the cell surface, and modulating
V
m
produces quantifiable and consistent changes in extracellular potential. Evidence strongly suggests this is due to capacitive coupling between
V
m
and the electrical double layer, rather than molecular transporters. We show that modulating
V
m
changes the extracellular ion composition, mimicking the behaviour if voltage-gated ion channels in non-excitable channels. We also observed
V
m
-synchronised circadian rhythms in extracellular potential, with significant implications for cell–cell interactions and cardiovascular disease.
