Identification of endocrine cells of the stomach that express acid-sensitive background potassium (K2P9.1/TASK3) channels

The family of two-pore domain potassium (K2P) channels is important in setting and controlling the background potassium current of excitable cells. This study examines the localisation of the acid-sensitive channel, K2P9.1 (TASK3), in cells of the gastric mucosa. We observed K2P9.1 immunoreactivity in endocrine cells of the mucosal glands of the guinea-pig, rat and mouse but the channels were not detected in parietal, chief, or mucous cells. K2P9.1 channel immunoreactivity was consistently co-localised with histidine decarboxylase immunopositive enterochromaffin-like (ECL) cells, and with the majority of ghrelin immunoreactive X/A cells. Localisation in somatostatin immunoreactive D cells was rare in the guinea-pig, and did not occur in the stomach of rat, but, in the mouse, K2P9.1 channels were observed in the majority of somatostatin-immunoreactive D cells. Conversely, sections taken from the guinea-pig and mouse stomachs, but not rat stomach, revealed K2P9.1 in gastrin-containing G cells. These results demonstrate the presence of K2P9.1 channels in the entero-endocrine ECL, G and D cell populations of the stomach that regulate acid secretion through the release of histamine, gastrin and somatostatin. K2P9.1 channels were located in the ghrelin X/A cells that regulate food intake.