| Objective: The lower esophageal sphincter (LES) is a thickened region of the circular muscle layer located at the gastroesophageal junctionin human, extending over an axial distance of 2–3 cm. Liebermann-Meffer et al proposed that musculature of equivalent of the LES consists of semicircular or clasp fibers at the lesser curvature and sling fibers at the greater curvature. These two muscle fibers and the crural diaphragm form a high-pressure zone at the gastroesophageal junction and maintain sphincter closure by which the LES forms an uniqe one-way valve. On the one hand, the continuous contraction of the LES prevents reflux of the gastric contents into the esophagus, but on the other hand, the proper relaxation of the LES permits passage of food from the esophagus into the stomach or to vomit and hiccup. The functional regulation of contraction and relaxation of the LES is very complicated, it involves nervous system, humoral factor and spontaneous myogenic factors.G proteins are important cellular parts in transmembrane signal transduction system, the majority of peptide hormones play an important role through G protein transduction pathways. In neurotransmitter substances, in addition to several amino acid neurotransmitters, the rest of the neurotransmitter substances completed signal transduction mainly by producing second messenger substances in postsynaptic cell . Some G protein which had been activated can also directly regulate the functional status of a number of channels to change membrane response. Different external signals carried out transmembrane signal by generating second messengers transduction in the membrane, which all required a similar structure of the various G protein-mediated. Motilin and gastrin activated Gi-3 protein in sinuses ventriculi smooth muscle cells of rats , and then rise to contraction of smooth muscle cells. Secretin induced relaxation in rat gastric smooth muscle cells mediated by the Gs protein. However, people at home and abroad researched LES regulatory mechanism mainly restricted to receptors, for the studying of G proteins, are relatively fewer. The existing human lower esophageal sphincter (LES) studies had mainly targeted animals (rats, etc.), which had species and physiological differences from human. There are no repor of the G protein expression pattern and regulation mechanism of the human LES of the relevant studies. This experiment used Western-blot to study expression of the G protein Gi-3, Go, Gq11, Gs subtypes in sling fibers, clasp fibers, esophageal circular muscle and gastric circular muscle. The aim of the study is to lay the foundation for the further study for human LES adjustment mechanism, and provided a theoretical basis for the treatment of esophageal motility disorders.Methods:1 Thirty patients including twenty-three males and seven females undergoing subtotal esophagectomy for middle thoracic esophageal carcinoma in our hospital between December 2008 and October 2009 were selected in this study. Fresh specimens were obtained from the gastroesophageal junction in the operating room. After the mucosa and submucosa were removed by sharp dissection, the sling and clasp fibers of LES, and circular muscle strips of esophagus and gastric were obtained from various regions of the gastroesophageal junction and adjacent structures.One hundred ul TBS reagent per ten mg of tissue was homogenated thoroughly with the tissue homogenizer, and then the homogenate was centrifuged at one thousand×g for ten minutes. The supernatant was discarded and the membrane receptor protein was obtained with the use of Membrane Protein Extraction. The membrane receptor was quantitated and adjusted to the identical concentration by Quantitative BCA ,then the four kinds of G protein subtypes were separated by electrophoresis. At last the detection of the protein expression was operated using G protein subtypes polyclonal antibody after the trarsmembrane. The IOD value was calculated with Gel-Pro softwere. Results:Western blot four kinds of G protein subtype had its corresponding expression of protein bands, namely, Gαq, Gαi-3, Gαo, Gαs,their molecular weight were 41kD, 45kD, 40kD, 48kD. IOD values of the same muscle strips with expression of different subtypes of in the clasp fibers (C) in the pairwise comparison, protein quantity of Gαi-3 express less than the protein quantity of Gαo, Gαq11, Gαs . There were no statistics differences on expression of protein quantity in the same subtype in all muscle strips .Conclusion:1. Four kinds of G protein subtypes in the clasp fibers (C), sling fibers (S), esophagus (E), gastric fundus (G) of the muscle strips are all expressed.2. The expression of four subtypes are different in a muscles strip.. Gαi-3 (C) expresses less than Gαo, Gαq11, Gαs in clasp fibers. There were no statistics differences in expression of the four G protein subtypes in the sling fibers (S) and circular muscles of the esophagus (E) and gastric fundus (G) .3. The expression of a subtyoe had no statistics difference in in all muscle strips.
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