The Role of Alpha-Adrenoceptor Subtype on Microvessels

血管平滑肌对α - ar介导的血管收缩的高反应性被认为是高血压状态下血管阻力升高维持的一个因素。α -AR的收缩可由α -1和α -2两种类型的α -AR介导。目前还没有确凿的证据表明α - ar亚型主要在高血压大鼠（SHR）的外周抵抗维持中起作用。采用体外视频显微镜观察高血压前期（4-5周）和高血压早期（7-8周）SHR患者与年龄变化的WKY患者的α - ar敏感性。用玻璃微管在组织浴中双管解剖血管。去甲肾上腺素（NE）浓度-反应曲线在吡唑嗪或秋狼碱存在下建立选择性刺激α -1或α -2 AR所需的NE浓度。在两个阶段，SHR对α -1收缩的敏感性都比WKY大得多。SHR和WKY在α -2收缩方面无差异。我们还研究了哪种α亚型对SHR中的肌源性调节更敏感。肌原性收缩在腔内压力下的α -2大于α -1。这些发现提示，α - ar对血管收缩的超敏反应在高血压患者血管阻力升高的维持或病因因素中起作用。

Hyperresponsiveness of vascular smooth muscle to alpha-AR-mediated vasoconstriction has been proposed as a factor involved in maintenance of the elevated vascular resistance in hypertensive state. alpha AR constriction can be mediated by two types of alpha-AR, alpha-1 and alpha-2. No conclusive evidence has been demonstrate in which subtype of alpha-AR playesmainly the role on maintenance of peripheral resistance in hypertensive rats (SHR). The sensitivity of alpha-AR of resistance large arteriole was examined with in vitro videomicroscopy in prehypertensive(4-5 week) and early hypertensive stage(7-8 week) of SHR compared with age mayched WKY. Microdissected vessels were double-cannulated with glass micropipets in a tissue bath. Norepinephrine (NE) concentration-response curves were obtained in the presence of prazosine or rauwolscine to establish the concentrations of NE required to selectivity stimulate alpha-1 or alpha-2 AR. The sensitivity to alpha-1 constriction was much greater in SHR than WKY in both stage. There was no difference in alpha-2 constriction between SHR and WKY. We also examined to explore which alpha subtype has a greater sensitivity to myogenic modulation in SHR. Myogenic constriction during in lumen pressure was greater during alpha-2 than alpha-1. These finding suggested that hypersensitivity of alphaAR to vasoconstriction play a role on maintenance or etiologic factor in elevated vascular resistance in hypertension.