Localization of ATP-sensitive K+ channel subunits in rat submandibular gland.

ATP-sensitive K(+) (K(ATP)) channel subunits were investigated in rat submandibular gland (SMG). RT-PCR detected the presence of mRNA transcripts of the Kir6.1, Kir6.2, SUR2A, and SUR2B in the SMG, whereas SUR1 mRNA was barely detected. Western blot analysis provided the evidence that these four K(ATP) channel subunits are expressed in rat SMG. Immunostaining detected that these four K(ATP) channel subunits are widely distributed, with different intensities, in myoepithelial cells, epithelial cells of intercalated ducts, granular convoluted tubules, striated ducts, and excretory ducts. Immunofluorescence double staining showed that Kir6.1 and Kir6.2 colocalized with SUR2A in the myoepithelial cells, granular convoluted tubules, striated ducts, and excretory ducts. Kir6.1 and Kir6.2 also colocalized with SUR2B, mainly in the duct system, e.g., the granular convoluted tubules, striated ducts, and excretory ducts. Taken together, these results indicate that the K(ATP) channels in SMG may consist of Kir6.1, Kir6.2, SUR2A, and SUR2B, with various combinations of colocalization with each other, and may play important roles in rat SMG during salivary secretion.