Prominent among the incompletely defined routes of basolateral K+ recycling in secretory epithelial cells and cultured ADPKD cyst epithelial cells is the KCNN4-encoded Ca2+-activated K+ channel of intermediate conductance, KCa3.1 (known in erythrocytes as the Gardos channel) (11–15). This evidence concerns the gene KCNN4 and autosomal dominant polycystic kidney disease.