Survival of K+ permeability and gating currents in squid axons perfused with K+-free media.

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Abstract
K+ currents were recorded in squid [L. pealei] axons internally perfused with impermeant electrolyte. Total absence of permeant ions inside and out leads to an irreversible loss of K+ conductance with a time constant of about 11 min at 8.degree. C. K+ channels can be protected against this effect by external K+, Cs+, NH4+ and Rb+ at concentrations of 100-440 mM. A K+ channel may normally be occupied by 1 or more small cations and may become nonfunctional when these cations are removed. A large charge movement related to K+ channel gating in frog skeletal muscle is absent in squid giant axons. Deliberate destruction of K+ conductance by removal of permeant cations is accompanied by measurable loss in asymmetric charge movement. This missing charge component is large enough to contain a contribution from K+ gating charge movements of more than 5 elementary charges/channel.