Concentration dependence of chloride movements that contribute to the conductance of the red cell membrane

Anion transport in red cells can be subdivided into two components; one that does not contribute to the conductance of the membrane and another that does. The former exceeds the latter about 104 fold (Harris & Pressman 1967, Scarpa et al. 1970, Hunter 1971, 1974, Tosteson et al. 1973). It is not clear whether the two forms of transport represent different aspects of the same transport mechanism or two unrelated pathways. In the former case, a rapid electrically silent” shuttling of the loaded form of the transport protein between the cis and trans conformation would be much faster than the rate of cis-trans transition of the unloaded form. In the latter case, a" conductance pathway" parallel and independent of the exchange pathway would be involved. The experiments depicted in Fig. 1 were designed to throw some light on the relationship between the two components