Abstract
We found that K+-Cl− cotransporter 4 (KCC4) was highly expressed in the luminal gastric parietal cells, in which gastric acid is actively secreted. To clarify distribution and function of KCC4 in gastric parietal cells, two types of gastric vesicles, stimulation-associated vesicles (SA) derived from surface apical membrane and intracellular tubulovesicles (TV), were prepared from hog gastric mucosa. KCC4 was predominantly expressed in SA but not in TV. Gastric proton pump (H+,K+-ATPase) was expressed both in SA and TV. KCC4 was co-immunoprecipitated with H+,K+-ATPase in the lysate of SA. Both KCC inhibitor (DIOA, 10 μM) and H+,K+-ATPase inhibitor (SCH 28080, 10 μM) significantly reduced the ATP-dependent Cl− uptake in SA by 78.0 ± 9.8% and 71.3 ± 11.8% respectively. The inhibition of DIOA plus SCH 28080 on the Cl− uptake was not additive, indicating that the Cl− transporting activity of KCC4 is positively regulated by H+,K+-ATPase. On the other hand, H+ uptake and ATP-hydrolyzing activity of H+,K+-ATPase in SA were significantly inhibited by DIOA (10 μM), suggesting that H+,K+-ATPase activity is positively regulated by KCC4. Thus, KCC4 and H+,K+-ATPase are functionally associated in SA. KCC4 may be involved in the basal gastric acid secretion of gastric parietal cells. [J Physiol Sci. 2008;58 Suppl:S54]
