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Angiotensin II‐induced contractions in human jejunal wall musculature in vitro
Author(s) -
Spak E.,
Casselbrant A.,
Olbers T.,
Lönroth H.,
Fändriks L.
Publication year - 2008
Publication title -
acta physiologica
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.591
H-Index - 116
eISSN - 1748-1716
pISSN - 1748-1708
DOI - 10.1111/j.1748-1716.2007.01826.x
Subject(s) - losartan , angiotensin ii , guanethidine , endocrinology , medicine , angiotensin receptor , myenteric plexus , renin–angiotensin system , tetrodotoxin , isometric exercise , contraction (grammar) , receptor , chemistry , biology , immunohistochemistry , stimulation , blood pressure
Aim: Angiotensin II is well known for its contractile effects on smooth muscle cells. This effect is also present in the gut previously shown in animal models. The aim of this study was to clarify expression and localization of angiotensin II receptors in the human small intestine and to explore the pharmacological profile of angiotensin II effects in vitro . Methods: Strips of jejunal muscle wall from 32 patients undergoing bariatric surgery were used to record isometric tension in vitro in response to angiotensin II (10 −10 –10 −5 m ) alone and in the presence of PD123319 (10 −7 m ), losartan (10 −7 m ), PD123319 (10 −7 m ) and losartan (10 −7 m ) in combination, tetrodotoxin (TTX) (10 −6 m ), atropine (10 −6 m ) and guanethidine (3 × 10 −6 m ). Western blot, immunohistochemistry and RT‐PCR were performed on corresponding muscle samples to identify expression and localization of key components of the renin–angiotensin system. Results: Angiotensin II elicited concentration‐dependent contraction in both longitudinal and circular jejunal muscle wall strips; neither TTX, atropine nor guanethidine affected this action. Losartan alone and in combination with PD123319 shifted the concentration–response curve to the right. Transcription of angiotensinogen, ACE and angiotensin II types 1 and 2 receptor RNA was detected in all patients. Immunohistochemistry detected angiotensin II type 1 receptors in the musculature; both angiotensin II types 1 and type 2 receptors were found in the myenteric plexus. Conclusion: This pharmacological analysis indicates that the contractile action elicited by angiotensin II on jejunal wall musculature is primarily mediated through the angiotensin II type 1 receptor located on the musculature.