Haemolytic anaemia associated with increased cation permeability.

Volume regulation in the red cell depends on the balance between the osmotic swelling pressure contributed by the polyvalent anions 2,3-DPG and haemoglobin, and the counterbalancing osmotic pressure provided by extracellular Na+. Although changes in 2,3-DPG have been identified in some cases, increases in the electrodiffusional leak of Na+ and K+ are most likely responsible for the disorders of volume regulation leading to haemolytic anaemia. The current challenge is to identify the membrane proteins and/or lipids which play a key role in passive transport of the monovalent cations.