A Teorell oscillator system with fine pore membranes.
A Teorell membrane oscillator system has been investigated theoretically and experimentally. Instead of the broad pore (e.g., glass sinter) membranes used by Teorell and other investigators, we used membranes of a hydrodynamic permeability lower by factor of 10(3)-10(5) and a fixed ion concentration higher by a factor of 10(2)-10(5). A system with such membranes was thought to be a more adequate analogue of excitable biological tissues (for which the Teorell oscillator had been presented as a model). Stationary state voltage-current curves were recorded, and flip-flops were only found in membranes whose hydrodynamic permeability was above a certain value. A theoretical description, agreeing closely with the experimental findings, is given in terms of the Nernst-Planck-Schlögl equations; flip-flops are predicted only if the hydrodynamic permeability is above the fixed ion concentration is below a critical value. These values depend on the hydrostatic pressure and on the ratio of the cation and anion diffusion coefficient in the membrane, and they are found to be far beyond (approximately 3 orders of magnitude) the data for membranes used by others in similar experiments. Although our theoretical analysis demonstrates that the Teorell mechanism is ineligible as a source of excitability in those biological systems for which sufficient data ate available to permit comparison, the membrane properties for which the theory predicts flip-flops are such that it cannot be excluded a priori.