A Hundred-Year Researching History on the Low Ionic Strength in Red Blood Cells: Literature Review

This review article provides a critical survey of work from 1904 to 2003 on the effects of low ionic strength in Red Blood Cells (RBCs) incubated in media with impermeable sugars such as sucrose. In 1904 Gürber A washed RBCs of different species with isotonic sucrose solution to eliminate the outside ions in order to better analyse their intracellular ionic composition; however, this approach was not feasible because of a substantial salt efflux from the cells. A prominent feature of the salt loss is the shrinking of the RBCs. A central role in the understanding of the ionic movements is thereby the new Donnan equilibrium of the anions. Experimental evidence has been given by Jacobs MH and Parpart AK in 1933. In the sucrose medium two phases could be predicted: 1) a very rapid anionic shift resulting in an unequal distribution of chloride and hydroxyl anions on both sides of the membrane and 2) a leakage of salts from the RBCs. In 1940 Wilbrandt W assumed that a positive membrane potential is in line with the salt loss at low ionic strength in RBCs. In 1977 Knauf PA, Fuhrmann GF, Rothstein S and Rothstein A observed in RBCs an inhibition of both, anion exchange and also of net anion efflux, by incubation with disulfonic stilbene derivates. At low ionic strength the Donnan equilibrium is immediately obtained by the Anion Exchanger Protein (AEP). The resulting positive membrane potential opens at least two new types of cation pores or channels. Thereby is the conductivity pathway for the anions, namely the AEP, in charge of the net anion loss at low ionic strength. The AEP pathway is extensively blocked by disulfonic stilbene compounds. The permeability ways for cations through these pores or channels are not yet explored.

Modeling the Effects of Intracellular Anions on Membrane Potential: An Active-Learning Exercise

In biological membranes that are permeable to water and ions but impermeable to other solutes, the diffusible ions cannot reach a concentration equilibrium. Instead, a state of electroneutrality is achieved on each side of the membrane, which requires that the diffusible ions be found in different concentrations on either side of the membrane. The Donnan equilibrium is a major contributing factor to the polarized state of cells, and appreciating it is vital to the understanding of neuronal physiology. This article presents a nonmathematical active-learning exercise that will help AP and college biology students understand how the Donnan equilibrium is achieved.

Interactions between amphoteric surfaces with strongly overlapping double layers

The entropic repulsion between strongly overlapping electrical double-layers from two parallel amphoteric plates is described via the Donnan equilibrium in the limit of zero electric field.

Impacts of inorganic draw solutes on the performance of thin-film composite forward osmosis membrane in a microfiltration assisted anaerobic osmotic membrane bioreactor

A Donnan equilibrium led to a higher NH4+–N concentration and more severe FO biofouling for the draw solutes NaCl and MgCl2, respectively.