Investigation of the distribution and function of α-adrenoceptors in the sheep isolated internal anal sphincter
Investigation of the distribution and function of α-adrenoceptors in the sheep isolated internal anal sphincter
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DOI：
10.1111/j.1476-5381.2010.00842.x
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发表时间：
2010-08-01
影响因子：
7.3
通讯作者：
Wilson, V. G.
中科院分区：
文献类型：
--
作者：
Rayment, S. J.;Eames, T.;Wilson, V. G.
背景和目的我们研究了作为人体组织模型的绵羊肛门内括约肌（IAS）中α-肾上腺素受体的分布，并评估了各种咪唑啉衍生物治疗大便失禁的潜力。实验方法使用3H-哌唑嗪和3H-RX821002的饱和和竞争结合来确认绵羊中α-肾上腺素受体的存在和密度IAS，以及咪唑啉化合物对这些受体的亲和力。结合体外受体放射自显影和免疫组织化学来研究结合位点的区域分布。通过等长张力记录评估基于咪唑啉的化合物对绵羊 IAS 的收缩活性。关键结果饱和结合证实了 α(1)- 和 α(2)- 肾上腺素受体的存在，随后用亚型选择剂进行表征，将它们鉴定为 α(1A)- 和 α(2D)- 肾上腺素受体亚型。 3H-哌唑嗪放射自显影研究表明，α(1)-肾上腺素受体与免疫组织化学鉴定的平滑肌纤维呈正相关。抗α(1)-肾上腺素受体免疫组织化学显示该受体在绵羊和人类 IAS 中的分布相似。咪唑啉化合物引起肛门括约肌的浓度依赖性收缩，但最大反应小于标准非咪唑啉α(1)-肾上腺素受体激动剂l-赤型甲氧胺引起的反应。哌唑嗪（选择性α(1)-肾上腺素受体拮抗剂）在最高使用浓度下显着降低了l-赤型甲氧胺的收缩幅度。哌唑嗪和 RX811059（一种选择性 α(2)- 肾上腺素受体拮抗剂）均降低可乐定的效力 (pEC(50))。 结论和意义本研究表明 α(1)- 和 α(2)- 肾上腺素受体在绵羊 IAS 中表达，并有助于（可能协同）各种咪唑啉衍生物引起的收缩。这些药物可能被证明可用于治疗大便失禁。
BACKGROUND AND PURPOSEWe have investigated the distribution of alpha-adrenoceptors in sheep internal anal sphincter (IAS), as a model for the human tissue, and evaluated various imidazoline derivatives for potential treatment of faecal incontinence.EXPERIMENTAL APPROACHSaturation and competition binding with 3H-prazosin and 3H-RX821002 were used to confirm the presence and density of alpha-adrenoceptors in sheep IAS, and the affinity of imidazoline compounds at these receptors. A combination of in vitro receptor autoradiography and immunohistochemistry was used to investigate the regional distribution of binding sites. Contractile activity of imidazoline-based compounds on sheep IAS was assessed by isometric tension recording.KEY RESULTSSaturation binding confirmed the presence of both alpha(1)- and alpha(2)-adrenoceptors, and subsequent characterization with sub-type-selective agents, identified them as alpha(1A)- and alpha(2D)-adrenoceptor sub-types. Autoradiographic studies with 3H-prazosin showed a positive association of alpha(1)-adrenoceptors with immunohistochemically identified smooth muscle fibres. Anti-alpha(1)-adrenoceptor immunohistochemistry revealed similar distributions of the receptor in sheep and human IAS. The imidazoline compounds caused concentration-dependent contractions of the anal sphincter, but the maximum responses were less than those elicited by l-erythro-methoxamine, a standard non-imidazoline alpha(1)-adrenoceptor agonist. Prazosin (selective alpha(1)-adrenoceptor antagonist) significantly reduced the magnitude of contraction to l-erythro-methoxamine at the highest concentration used. Both prazosin and RX811059 (a selective alpha(2)-adrenoceptor antagonist) reduced the potency (pEC(50)) of clonidine.CONCLUSIONS AND IMPLICATIONSThis study shows that both alpha(1)- and alpha(2)-adrenoceptors are expressed in the sheep IAS, and contribute (perhaps synergistically) to contractions elicited by various imidazoline derivatives. These agents may prove useful in the treatment of faecal incontinence.