KCNN4 and ulcerative colitis: For example, in ulcerative colitis (UC), the number of KCa3.1 channels present at the plasma membrane is reduced while membrane KCa3.1 channels are increased in polycystic kidney disease (PKD) resulting in increased fluid in patients with PKD (Albaqumi et al., 2008; Al-Hazza et al., 2012).