A Ca2+-refractory state of the Ca-sensitive K+ permeability mechanism in sickle cell anaemia red cells

Simultaneous measurements of Ca content and 42K+ influx in sickle cell anaemia red cells confirm predictions from earlier data in the literature that the increased Ca content of sickle cell anaemia cells which are not metabolically depleted does not cause a quinine-sensitive increase in K+ permeability. It is shown that the ionophore, A23187, can cause the Ca contained inside sickle cell anaemia cells to activate the quinine-sensitive K+-permeability mechanism. This demonstrates the existence of a Ca2+-refractory state of the K+ channel in sickle cell anaemia cells and a direct stimulatory effect of the ionophore A23187 on its Ca sensitivity.