Messenger RNA levels and binding sites of muscarinic acetylcholine receptors in gastrointestinal muscle layers from healthy dairy cows

Ontsouka, E C; Bruckmaier, R M; Steiner, A; Blum, J W; Meylan, M (2007). Messenger RNA levels and binding sites of muscarinic acetylcholine receptors in gastrointestinal muscle layers from healthy dairy cows. Journal of receptor and signal transduction research, 27(2-3), pp. 147-66. New York, N.Y.: Marcel Dekker 10.1080/10799890701417741

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Acetylcholine interacts with muscarinic receptors (M) to mediate gastrointestinal (GI) smooth muscle contractions. We have compared mRNA levels and binding sites of M(1)to M(5) in muscle tissues from fundus abomasi, pylorus, ileum, cecum, proximal loop of the ascending colon (PLAC), and external loop of the spiral colon (ELSC) of healthy dairy cows. The mRNA levels were measured by quantitative RT-PCR. The inhibition of [(3)H]-QNB (1-quinuclidinyl-[phenyl-4-(3)H]-benzilate) binding by M antagonists [atropine (M(1 - 5)), pirenzepine (M(1)), methoctramine (M(2)), 4-DAMP (M(3)), and tropicamide (M(4))] was used to identify receptors at the functional level. Maximal binding (B(max)) was determined through saturation binding with atropine as a competitor. The mRNA levels of M(1), M(2), M(3), and M(5) represented 0.2, 48, 50, and 1.8%, respectively, of the total M population, whereas mRNA of M(4) was undetectable. The mRNA levels of M(2) and of M(3) in the ileum were lower (P < 0.05) than in other GI locations, which were similar among each other. Atropine, pirenzepine, methoctramine, and 4-DAMP inhibited [(3)H]-QNB binding according to an either low- or high-affinity receptor pattern, whereas tropicamide had no effect on [(3)H]-QNB binding. The [(3)H]-QNB binding was dose-dependent and saturable. B(max) in fundus, pylorus, and PLAC was lower (P < 0.05) than in the ELSC, and in the pylorus lower (P < 0.05) than in the ileum. B(max) and mRNA levels were negatively correlated (r = -0.3; P < 0.05). In conclusion, densities of M are different among GI locations, suggesting variable importance of M for digestive functions along the GI tract.

Item Type:

Journal Article (Original Article)

Division/Institute:

05 Veterinary Medicine > Department of Clinical Research and Veterinary Public Health (DCR-VPH) > Veterinary Physiology
05 Veterinary Medicine > Department of Clinical Veterinary Medicine (DKV) > Clinic for Ruminants

UniBE Contributor:

Ontsouka, Corneille Edgar; Bruckmaier, Rupert; Steiner, Adrian; Blum, Jürg and Meylan, Mireille

ISSN:

1079-9893

Publisher:

Marcel Dekker

Language:

English

Submitter:

Factscience Import

Date Deposited:

04 Oct 2013 14:53

Last Modified:

21 Jan 2014 15:05

Publisher DOI:

10.1080/10799890701417741

PubMed ID:

17613726

Web of Science ID:

000248080400004

URI:

https://boris.unibe.ch/id/eprint/22710 (FactScience: 36118)

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