In the resting state of the parietal cell, H+,K+-ATPase is located in so-called tubulovesicles beneath the luminal membrane and is functionally silent. At the present time, it is not known whether H+,K+-ATPase and K+ channels are located in the same tubulovesicles. Upon stimulation of gastric acid secretion, K+ channels (probably KCNE2/KCNQ1, KCNJ1, KCNJ2 and KCNJ10) are activated via cAMP and other pathways, resulting in KCl secretion. H+,K+-ATPase is predominantly targeted to the luminal pole of canaliculi, where it pumps out H+ in exchange for K+.