Department of Clinical Experimental Research, Glostrup Research Institute, Glostrup Hospital, University of Copenhagen, Copenhagen, Denmark; Department of Drug Design and Pharmacology, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark.
Br J Pharmacol. 2014 Jun;171(11):2726-38. doi: 10.1111/bph.12606.
Endothelins act via two receptor subtypes, ETA and ETB . Under physiological conditions in coronary arteries, ETA receptors expressed in smooth muscle cells mediate vasoconstriction whereas ETB receptors mainly found in endothelial cells mediate vasorelaxation. However, under pathophysiological conditions, ETB receptors may also be expressed in vascular smooth muscle cells mediating vasoconstriction. Here, we have investigated whether vasoconstrictor ETB receptors are up-regulated in coronary arteries after experimental myocardial ischaemia in rats.
Male Sprague-Dawley rats were subjected to either heart ischaemia-reperfusion (15 min ischaemia and 22 h reperfusion), permanent ischaemia (22 h) by ligation of the left anterior descending coronary artery, or sham operation. Using wire myography, the endothelin receptor subtypes mediating vasoconstriction were examined in isolated segments of the left anterior descending and the non-ligated septal coronary arteries. Endothelin receptor-mediated vasoconstriction was examined with cumulative administration of sarafotoxin 6c (ETB receptor agonist) and endothelin-1 (with or without ETA or ETB receptor blockade). The distribution of ETB receptors was localized with immunohistochemistry and quantified by Western blot.
Endothelin ETB receptor-mediated vasoconstriction and receptor protein levels were significantly augmented in coronary arteries situated downstream of the occlusion after ischaemia-reperfusion compared with non-ischaemic arteries. In contrast, the ETA receptor-mediated vasoconstriction was unaltered in all groups.
Ischaemia-reperfusion induced local up-regulation of ETB receptors in the smooth muscle cells of coronary arteries in the post-ischaemic area. In contrast, in non-ischaemic areas, ETB receptor function was unaltered.
内皮素通过两种受体亚型ETA 和 ETB 发挥作用。在冠状动脉的生理条件下，平滑肌细胞中表达的 ETA 受体介导血管收缩，而主要存在于内皮细胞中的 ETB 受体介导血管舒张。然而，在病理生理条件下，ETB 受体也可能在血管平滑肌细胞中表达，介导血管收缩。在这里，我们研究了在大鼠实验性心肌缺血后，冠状动脉中收缩性 ETB 受体是否上调。
雄性 Sprague-Dawley 大鼠接受心脏缺血再灌注（缺血 15 分钟，再灌注 22 小时）、左前降支冠状动脉结扎引起的永久性缺血（22 小时）或假手术。使用线描记术，在左前降支和非结扎间隔冠状动脉的分离段中检查介导血管收缩的内皮素受体亚型。用沙夫托毒素 6c（ETB 受体激动剂）和内皮素-1（有或没有 ETA 或 ETB 受体阻断）累积给药来检查内皮素受体介导的血管收缩。用免疫组织化学定位 ETB 受体，并通过 Western blot 进行定量。
与非缺血动脉相比，缺血再灌注后闭塞下游的冠状动脉中内皮素 ETB 受体介导的血管收缩和受体蛋白水平显著增加。相比之下，所有组的 ETA 受体介导的血管收缩均未改变。
缺血再灌注诱导缺血后区域的冠状动脉平滑肌细胞中 ETB 受体的局部上调。相比之下，在非缺血区域，ETB 受体功能未改变。
