To detect the distribution of endothelin receptors(ETR) in the human lower esophageal sphincter (LES), especially on the clasp and sling smooth muscle fibers of the LES, and investigate the effects of endothelins on the contraction and diastole of LES.

The sling and clasp tissues from LES were obtained from esophageal carcinoma patients, and the circular muscle tissues from the esophagus and gastric fundus were served as controls. Western Blot, RT-PCR and semi-qPCR were employed to determine the distribution of ETR in human LES.

Endothelin receptor type A (ETA) and endothelin receptor type B (ETB) were found in human LES. There were significant differences in the expression of protein and mRNA between two isoforms of ETR (F=533.841, P<0.01; F=72.291, P<0.01). The expression level of ETA was significantly higher than that of ETB(about 5: 1). For distribution of each isoform, there was no significant difference in the expression level among four sites of clasp fibers(C), sling fibers(S), lower esophageal sphincter(E) and gastric fundus circular muscle(G)(F=0.398, P=0.5329).

ETRs contribute to the adjustment of contraction and diastole of human LES, especially the ETA. ETRs are the potent therapeutic targets for esophageal mobility diseases.