ANALYSIS OF MEMBRANE PERMEABILITY COEFFICIENTS OF AMPHIBIAN SKIN BY MEANS OF ELECTRONIC DATA PROCESSING: I. A NEW CONSTANT FIELD EQUATION APPLICABLE TO AMPHIBIAN SKIN POTENTIAL

A new extended membrane equation applicable to carriermediated active transport is derived, as follows: _??_ where ΔE is membrane potential, ψ and Φ correspond to active-transport flux and carrier-mediated flux respectively, and other notations have their usual meanings in membrane equations. By means of electronic data processing, such an extended membrane equation is applicable to computation of the ion permeability coefficients of the skin of frog, toad, and newt using a least-square method. Applying the two-membrane theory of Ussing, the membrane potential of the amphibian skin is obtained as follows: _??_ and _??_ These relations show a fairly good respective agreement with the observed potentials. Application of such an extended equation not only avoids the appearance of a physiologically meaningless negative permeability coefficient for some one of the ions, as is often obtained by applying the original Goldman equation, but also results in a fairly reasonable value for these coefficients.