Potassium transport in epithelial cells isolated from small intestine of the chicken

The transport of potassium has been studied in epithelial cells isolated from chicken small intestine using 86Rb as a tracer for K+. (i) The uptake studies revealed that about 60% of the total K+ net flux is inhibited by ouabain and therefore mediated by the Na+-K+-ATPase. About 20% of the ouabain-insensitive K+ net influx was inhibited by furosemide, bumetanide and by either Na+ or Cl- removal from the incubation solution, suggesting that a Na+/Cl-/K+ cotransport system might be present in chicken enterocytes. (ii) The efflux of K+ was measured from cells preloaded with 86Rb. K+ efflux was inhibited by Ba2+, quinine and verapamil; it was stimulated by A23187, and it was unaffected by 3,4-diaminopyridine. Apamin, that has no effect on basal rates of K+ efflux, abolished the effect of A23187. These findings suggest that K+ efflux appears to occur through Ca2+-activated K+ channels.