Identification of GIRK2-4 subunits in human esophageal smooth muscle cells

Acetylcholine (ACh) secreted from the vagus nerve contributes to the physiological and pathological regulation of the contraction and relaxation of human esophageal smooth muscle. Expression of acetylcholine-sensitive G protein‑activated inwardly rectifying potassium channels (GIRKs) occurs widely in the heart, nervous system and gastrointestine, but the role of GIRKs in the esophagus remains unclear. In the present study, expression of the GIRK1-4 subunits in mRNA and total protein was examined in human esophageal smooth muscle cells (SMCs) by reverse transcription polymerase chain reaction (RT-PCR) and Western blotting. mRNA and protein expression of the GIRK2-4 subunits was detected in human esophageal longitudinal muscle (LM) and circular muscle (CM) cells. However, GIRK1 mRNA and protein were not observed in either the esophageal LM or CM. This study is the first to identify the expression of GIRK2-4 subunits in human esophageal SMCs.