血管平滑肌α -肾上腺素受体:均不正常。

Blood vessels Pub Date : 1991-01-01 DOI:10.1159/000158849
E E Daniel, A G Shi, Z L Wang, Y Y Guan, K Hoo, E J Cragoe, C Y Kwan
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引用次数: 15

摘要

血管肌对α 1-和α 2-肾上腺素受体的结合相互作用和收缩反应的研究揭示了以下几点。(1) α 1-和α 2-肾上腺素受体的激动剂虽然在两种受体上具有相似的亲和性,但由于其不同的功效,可能实现选择性。这意味着它们在结合研究中的效力可能与反应的效力无关,并且激动剂可能通过占据α 1-和α 2受体而产生积极或消极的相互作用。(2) α 2-肾上腺素受体激动剂在一些血管肌肉中具有释放内部Ca2+(暗示肌醇三磷酸机制)和打开Ca2+通道的能力。然而,它们的收缩能力与Na+/H+或Na+/Ca2+交换位点的功能并不密切相关。阿米洛利衍生物可能通过受体或钙通道远端的作用抑制α激动剂的收缩作用和K+升高。(3) α - 2激动剂在体外收缩动脉的失败与缺乏这些受体无关,而最有可能是它们从收缩反应中解耦,这可能是由于与体外条件相关的变化(体内存在的调节内源性物质的丧失,如血管紧张素II或内皮素,或改变的物理条件,如可能改变拉伸激活通道的功能)。
本文章由计算机程序翻译,如有差异,请以英文原文为准。
Alpha-adrenoceptors in vascular smooth muscle: all is not well.

Studies of binding interactions and contractile responses of vascular muscles at alpha 1- and alpha 2-adrenoceptors revealed the following. (1) Agonists at alpha 1- and alpha 2-adrenoceptors may achieve selectivity by virtue of different efficacies despite similar affinities at the two receptors as well as by differing affinities. This implies that their potencies in binding studies may not correlate with potencies in response and that an agonist may produce positive or negative interactions by occupying both alpha 1- and alpha 2-receptors. (2) Agonists at alpha 2-adrenoceptors have the ability in some vascular muscles to release internal Ca2+ (implying an inositol triphosphate mechanism) as well as open Ca2+ channels. However, their contractile abilities are not closely related to function of Na+/H+ or Na+/Ca2+ exchange sites. Amiloride derivatives probably inhibit contractile effects of alpha-agonists and K+ elevation by an action at sites distal to the receptor or Ca channels. (3) The failure of alpha 2-agonists to contract arteries in vitro is not related to the absence of these receptors but most likely to their uncoupling from contractile responses, possibly owing to changes related to the in vitro condition (loss of modulating endogenous substances present in vivo such as angiotensin II or endothelins or to changed physical conditions such as may alter function of stretch-activated channels).

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