Research Report
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World J Gastroenterol. Jun 7, 2014; 20(21): 6554-6559
Published online Jun 7, 2014. doi: 10.3748/wjg.v20.i21.6554
Investigation of cholecystokinin receptors in the human lower esophageal sphincter
Jun-Feng Liu, Jian Zhang, Xin-Bo Liu, Paul A Drew
Jun-Feng Liu, Jian Zhang, Xin-Bo Liu, Department of Thoracic Surgery, Fourth Hospital, Hebei Medical University, Shijiazhuang 050011, Hebei Province, China
Paul A Drew, School of Nursing and Midwifery, Flinders University, Adelaide 5001, Australia
Author contributions: Liu JF designed the study; Zhang J performed the experiments; all authors assisted in data interpretation, drafting and revising the manuscript.
Supported by Government Foundation Grant from Hebei Provincial Department of Education, No. HBGX2005-52; and National Natural Science Foundation of China, No. 30371413
Correspondence to: Jun-Feng Liu, PhD, Professor, Department of Thoracic Surgery, Fourth Hospital, Hebei Medical University, 12 Jiankang Road, Shijiazhuang 050011, Hebei Province, China. liujf@heinfo.net
Telephone: +86-311-86095353 Fax: +86-311-86077634
Received: June 13, 2013
Revised: September 27, 2013
Accepted: November 3, 2013
Published online: June 7, 2014
Processing time: 357 Days and 18 Hours
Abstract

AIM: To compare the binding of cholecystokinin (CCK)-8 to CCK receptors in sling and clasp fibers of the human lower esophageal sphincter.

METHODS: Esophageal sling and clasp fibers were isolated from eight esophagectomy specimens, resected for squamous cell carcinoma in the upper two thirds of the esophagus, which had been maintained in oxygenated Kreb’s solution. Western blot was used to measure CCK-A and CCK-B receptor subtypes in the two muscles. A radioligand binding assay was used to determine the binding parameters of 3H-CCK-8S to the CCK receptor subtypes. The specificity of binding was determined by the addition of proglumide, which blocks the binding of CCK to both receptor subtypes.

RESULTS: There was no significant difference between the sling and clasp fibers of the human lower esophageal sphincter in the amount of CCK-A [integrated optical density (IOD) value: 22.65 ± 0.642 vs 22.328 ± 1.042, P = 0.806] or CCK-B receptor protein (IOD value: 13.20 ± 0.423 vs 12.45 ± 0.294, P = 0.224) as measured by Western blot. The maximum binding of radio-labeled CCK-8S was higher in the sling fibers than in the clasp fibers (595.75 ± 3.231 cpm vs 500.000 ± 10.087 cpm, P < 0.001) and dissociation constant was lower (Kd: 1.437 ± 0.024 nmol/L vs 1.671 ± 0.024 nmol/L, P < 0.001). The IC50 of the receptor specific antagonists were lower for the CCK-A receptors than for the CCK-B (P < 0.01).

CONCLUSION: CCK binding modulates the contractile function of the lower esophageal sphincter through differential binding to the CCK-A receptor on the sling and clasp fibers.

Keywords: Cholecystokinins; Cholecystokinins-A receptor; Cholecystokinins-B receptor; Radioligand binding; Lower esophageal sphincter; Sling fibers; Clasp fibers

Core tip: We isolated the sling and clasp muscles which help form the human lower esophageal sphincter. The expression of cholecystokinin (CCK)-A and CCK-B receptors was measured in the two muscles. The binding of 3H-CCK-8S to the CCK receptors was studied to determine the binding characteristics of the hormone to the receptor subtypes. It is concluded that the CCK-A receptor probably plays a more important role than the CCK-B receptor in mediating the contractile function of lower esophageal sphincter, through a combination of more receptors and a stronger binding affinity.