Mechanism and regulation of transcellular potassium transport by the colon.

The mechanisms by which the colon handles potassium have been the subject of controversy for several years. However, recent studies have provided compelling evidence supporting the presence of active transcellular mechanisms for potassium transport by the colon. These studies have demonstrated that active uptake mechanisms for potassium exist at both the apical and basolateral membranes. Thus, depending on the conditions or the segment of colon studied, both active potassium absorption and secretion can be demonstrated. In addition, results have been obtained demonstrating that active potassium transport by the colon is regulated by endogenous mediators via modulation of intracellular cAMP and/or calcium levels. However, the mechanisms by which potassium exits across either cell membrane and the mechanisms by which intracellular mediators regulate active potassium uptake processes and/or potassium exit are not well understood.