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Characterization of alpha-adrenoceptor subtypes in smooth muscle of equine ileum.
Abstract: To determine the concentration and binding characteristics of alpha-adrenoceptor subtypes in smooth muscle cell membranes of equine ileum. Methods: Segments of longitudinal and circular smooth muscle from the ileum of 8 male and 8 female adult horses. Methods: Distribution of alpha-adrenoceptor subtypes was assessed by use of radioligand binding assays incorporating [3H]-prazosin and [3H]-rauwolscine, highly selective alpha1- and alpha2-adrenoceptor antagonists, respectively. Characterization of adrenoceptor subtypes was performed by use of binding inhibition assays. Results: On the basis of binding affinity for specific radioligands, low- and high-affinity alpha1- and alpha2-adrenoceptors were detected. Concentration of low-affinity alpha2-adrenoceptors was significantly greater in male horses, compared with females. Competition studies confirmed the specificity of the radioligands used in the binding assays. Alpha1-adrenoceptors of both subtypes in male and female horses had a higher affinity for prazosin than phentolamine, whereas yohimbine did not compete with the radioligand for binding. For alpha2-adrenoceptors regardless of subtype, potency of inhibition elicited by each drug varied between sexes. In males, yohimbine was a more potent inhibitor than phentolamine, which was more potent than prazosin. In females, yohimbine was more potent than prazosin, which was more potent than phentolamine. Conclusions: High- and low-affinity alpha1- and alpha2-adrenoceptors were detected in smooth muscle of equine ileum. Because alpha-adrenoceptor subtypes, particularly alpha2-adrenoceptors, are involved in the regulation of gastrointestinal tract function, characterization of these receptors may represent the basis for development of new therapeutic strategies for the control of gastrointestinal disturbances in horses.
Publication Date: 2001-09-19 PubMed ID: 11560262DOI: 10.2460/ajvr.2001.62.1370Google Scholar: Lookup The Equine Research Bank provides access to a large database of publicly available scientific literature. Inclusion in the Research Bank does not imply endorsement of study methods or findings by Mad Barn.
- Journal Article
- Research Support
- Non-U.S. Gov't
Summary
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The study investigates the concentration and binding characteristics of alpha-adrenoceptor subtypes in the smooth muscle of the ileum, a part of the intestinal tract in horses. It highlights how the alpha-adrenoceptor subtypes, specifically alpha2-adrenoceptors, play a significant role in controlling gastrointestinal function in horses.
Methods
- The study involved the extraction of segments of longitudinal and circular smooth muscle from the ileum (part of the intestines) of 8 adult male and 8 adult female horses.
- The researchers then used radioligand binding assays, that incorporates [3H]-prazosin and [3H]-rauwolscine. These are highly selective alpha1- and alpha2-adrenoceptor antagonists, respectively, used to determine the distribution of alpha-adrenoceptor subtypes.
- Characterization of these adrenoceptor subtypes was carried out through binding inhibition assays.
Results
- The study found both low- and high-affinity alpha1- and alpha2-adrenoceptors based on their binding affinity for specific radioligands.
- The concentration of low-affinity alpha2-adrenoceptors was found to be greater in male horses as opposed to females.
- Competition studies confirmed the specificity of the radioligands used.
- In both male and female horses, alpha1-adrenoceptors of both subtypes showed a higher affinity for the drug prazosin than for phentolamine, while yohimbine didn’t compete with the radioligand for binding.
- For alpha2-adrenoceptors, regardless of subtype, the potency of inhibition elicited by each drug was found to vary between sexes. In males, yohimbine was a more potent inhibitor than phentolamine, which was more potent than prazosin. In females, yohimbine was more potent than prazosin, which was more potent than phentolamine.
Conclusion
- The study successfully detected high- and low-affinity alpha1- and alpha2-adrenoceptors in the smooth muscle of the equine ileum.
- The findings are significant as alpha-adrenoceptor subtypes, particularly alpha2-adrenoceptors, are involved in the regulation of gastrointestinal tract function.
- Understanding the nature and function of these receptors could potentially form the basis for the development of new therapeutic strategies to deal with gastrointestinal disturbances in horses.
Cite This Article
APA
Re G, Badino P, Odore R, Galaverna D, Girardi C.
(2001).
Characterization of alpha-adrenoceptor subtypes in smooth muscle of equine ileum.
Am J Vet Res, 62(9), 1370-1374.
https://doi.org/10.2460/ajvr.2001.62.1370 Publication
Researcher Affiliations
- Department of Animal Pathology, University of Turin, Italy.
MeSH Terms
- Adrenergic alpha-Antagonists / pharmacology
- Animals
- Binding Sites / physiology
- Female
- Horses / metabolism
- Ileum / chemistry
- Ileum / drug effects
- Ileum / metabolism
- Male
- Muscle, Smooth / chemistry
- Muscle, Smooth / drug effects
- Muscle, Smooth / metabolism
- Phentolamine / pharmacology
- Prazosin / pharmacology
- Receptors, Adrenergic, alpha / classification
- Receptors, Adrenergic, alpha / metabolism
- Yohimbine / pharmacology
Citations
This article has been cited 2 times.- Verhaar N, Hoppe S, Grages AM, Hansen K, Neudeck S, Kästner S, Mazzuoli-Weber G. Dexmedetomidine Has Differential Effects on the Contractility of Equine Jejunal Smooth Muscle Layers In Vitro. Animals (Basel) 2023 Mar 10;13(6).
- Re G, Badino P, Odore R, Zizzadoro C, Ormas P, Girardi C, Belloli C. Identification of functional alpha-adrenoceptor subtypes in the bovine female genital tract during different phases of the oestrous cycle. Vet Res Commun 2002 Aug;26(6):479-94.
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