Expression and function of colonic epithelial K(v)LQT1 K+ channels

1. K(V)LQT1 (KCNQ1) is a voltage-gated K+ channel essential for repolarizat ion of the heart action potential Defects in ion channels have been demonst rated in cardiac arrhythmia. This channel is inhibited potently by the chro manol 293B, The same compound has been shown to block cAMP-dependent electr olyte secretion in rat and human colon, Therefore, it was suggested that a K+ channel similar to K(V)LQT1 is expressed in the colonic epithelium. 2, In the present paper, expression of K(V)LQT1 and its function in colonic epithelial cells is described. Reverse transcription-polymerase chain reac tion analysis of rat colonic mucosa demonstrated expression of K(V)LQT1 in both crypt cells and surface epithelium. When expressed in Xenopus oocytes, K(V)LQT1 induced a typical delayed activated K+ current. 3, As demonstrated, the channel activity could be further activated by incr eases in intracellular cAMP. These and other data support the concept that K(V)LQT1 is forming a component of the basolateral cAMP-activated Kf conduc tance in the colonic epithelium.