A chemically unmasked, chloride dependent K+ transport in low K+ sheep red cells: genetic and evolutionary aspects

Recent evidence for a chemically unmasked, Cl- dependent K+ transport system present in LK sheep red cells has been reviewed. Exposure of LK cells to millimolar concentrations of N-ethylmaleimide (NEM) caused an up to 10 fold increase of a Cl- dependent K+ permeability with saturation kinetics and a low K+ affinity. Genetically associated with the expression of the LK gene, the chemically uncovered, Cl- activated K+ flux resembles evolutionary ancient cation transport systems found in nucleated red cells and non-erythrocytic mammalian cells. Perhaps the K+ transport system here described may play a significant role in volume reduction when sheep reticulocytes "mature" to adult red cells.