KCNN4 and cystic fibrosis: RT-PCR analyses demonstrated that transcripts encoding for the clotrimazole-sensitive Ca2+-activated K+ channel KCNN4, which is pharmacologically activated by 1-EBIO and responsible for driving Ca2+-activated Cl− in mouse colon [22], [23], [31], are expressed in native rectal tissues from control subjects and CF patients (Fig. 2 E).