A theory of the saturable ohmic channel.

Let the passage of type-lambda ions through a type-sigma channel be determined only by the ionic valence z lambda, by the thermal energy kT, by the ion concentrations on the out- and in- sides [S lambda]o and [S lambda]i, by the inside with-respect-to outside voltage of the channel E, by a single descriptor of channel saturation [S sigma lambda], and by a single descriptor (permeance) the ease of channel transit P sigma lambda. Then, if the channel current i sigma lambda, due to lambda-ions is ohmic about the Nernst potential, is a function of the sum ([S lambda]o + [S lambda]i) and not of [S lambda]o or [S lambda]i independently, and saturates in a Michaelis-Menten fashion, it follows that (Formula: see text) where F is the Faraday constant.