Parallel intermediate conductance K+ (IK) and Cl- (CLC2) channel activity mediates electroneutral K+ exit across basolateral membranes in rat distal colon.

Parallel intermediate conductance K+ (IK) and Cl- (CLC2) channel activity mediates electroneutral K+ exit across basolateral membranes in rat distal colon. Am J Physiol Gastrointest Liver Physiol. 2020 Jun 22;: Authors: Rehman SM, Narayanan K, Nickerson AJ, Coon SD, Hoque KM, Sandle GI, Rajendran VM Abstract Transepithelial K+ absorption requires apical K+ uptake and basolateral K+ exit. In colon, apical H+,K+-ATPase mediates cellular K+ uptake, and it has been suggested that electroneutral basolateral K+ exit reflects K+-Cl- cotransporter-1 (KCC1) operating in parallel with K+ and Cl- channels. Present study was designed to identify basolateral transporter(s) responsible for K+ exit in rat distal colon. Active K+ absorption was determined by measuring 86Rb+ (K+ surrogate) fluxes in colonic epithelia mounted under voltage clamp conditions. With zero Cl- in the mucosal solution, net K+ absorption was reduced by 38%, indicating that K+ absorption was, at least in part, Cl--dependent. Addition to the serosal solution of DIOA (KCC1 inhibitor) and Ba2+ (non-specific K+ channel blocker) inhibited net K+ absorption by 21% and 61% respectively, suggesting that both KCC1 and K+ channels contribute to basolateral K+ exit. Serosal addition of clotrimazole and TRAM34 (IK channel blockers) inhibited net K+ absorption, pointing to the involvement of IK channels in basolateral K+ exit. Serosal addition of GaTx2 (CLC2 blocker) also inhibited net K+ ...
Source: Am J Physiol Gastroi... - Category: Gastroenterology Authors: Tags: Am J Physiol Gastrointest Liver Physiol Source Type: research