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 using⁸⁶Rb 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 with⁸⁶Rb. 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.