Dynamic Interfacial Electrochemical Phenomena at Living Cell Membranes: Application to the Toad Urinary Bladder Membrane System

The concept of electrochemical information transfer in vivo has been studied using the isolated toad urinary bladder membrane system to evaluate a recently developed approach to membrane impedance which emphasized the coupling of interfacial processes to standard transport phenomena. Laplace plane analysis was utilized to examine frequency response from 1 Hz to 1 MHz. The results indicate that, under the linear conditions of this experiment, Na+ ion is the predominant current carrier and that the rate-determining step is its penetration into the membrane phase from the aqueous phase. Thus, membrane transport appears to be a very rapid step, whereas the interfacial step of phase transfer regulates transport in this system. The implication of this result in terms of potential dependent interfacial steps in the control of cellular function is discussed.