Actions by Angiotensin II on Esophageal Contractility in Humans

Abstract

Background & Aims: Angiotensin II is a potent activator of smooth muscles but has not been much investigated with regard to gastrointestinal motor activity. This study explores expression of the renin-angiotensin system (RAS) in human esophageal musculature and actions by Angiotensin II both in vitro and in vivo. Methods: Muscular specimens of esophageal body and lower esophageal sphincter were obtained from patients undergoing resection as a result of mucosal neoplasm. Healthy volunteers participated in functional examinations of esophageal motility assessed by high-resolution manometry and multiple transmucosal potential-difference measurements. Results: Gene transcripts of key components of RAS were found in the esophageal musculature. Immunohistochemistry revealed a distinct staining for Angiotensin II type 1 (AT1) receptors in the muscular bundles and blood-vessel walls, whereas Angiotensin II type 2 receptors were confined to blood vessels only. Angiotensin II caused concentration-dependent contractions in vitro, which were inhibited by the AT1 receptor antagonist losartan but not by the Angiotensin II type 2 receptor antagonist PD123319. Administration of the AT1 receptor antagonist candesartan reduced the amplitude of swallow-induced peristaltic contractions and both the length and pressure amplitude of baseline high-pressure zone at the esophagogastric junction. Neither swallow-induced axial movements, nor the contraction after transient lower esophageal sphincter relaxations, were influenced by candesartan pretreatment. Conclusions: The study demonstrates a local RAS in the musculature of the distal esophagus and that Angiotensin II is a potent stimulator of esophageal contractions via the AT1 receptor. The results suggest that Angiotensin II participates in the physiological control of the human esophageal motor activity. © 2007 AGA Institute.