In vitro analysis of alpha-adrenoceptor interactions with the myogenic response in resistance vessels.
In vitro analysis of alpha-adrenoceptor interactions with the myogenic response in resistance vessels.
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α-肾上腺素受体与阻力血管生肌反应相互作用的体外分析。
DOI：
10.1159/000158946
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发表时间：
1992
影响因子：
1.7
通讯作者：
Faber,JE
中科院分区：
文献类型：
--
作者：
Ikeoka,K;Nishigaki,K;Ohyanagi,M;Faber,JE
用体外视频显微镜检查离体大鼠提睾小动脉（平均直径±SEM，114±5μm）的α1-和α2-肾上腺素受体收缩与生肌机制的相互作用。在组织浴中用玻璃微量移液管对显微解剖的血管进行双插管，并将管腔内压力设置为 65 mm Hg 基线压力。单独获得去甲肾上腺素 (NE) 浓度-反应曲线，并在哌唑嗪或萝芙素存在下获得，以确定选择性刺激 α1- 或 α2- 肾上腺素受体所需的 NE 浓度。 NE 单独产生双峰反应，表明与多个受体群体相互作用。萝芙素和哌唑嗪在低 NE 浓度（<0.1 µM）下均产生右旋位移。然而，虽然哌唑嗪表现出竞争性拮抗作用，但萝芙素在浓度≧ EC50值时并不拮抗NE。因此，α1 和 α2 肾上腺素受体在低 NE 浓度下介导收缩，但只有 α1 受体在中浓度和高浓度下介导收缩。这些数据与之前在体内研究的相同血管的发现形成对比。在硝普钠存在的松弛（被动）状态下、自发内在张力期间以及诱导α1-或α2-张力期间（NE加萝芙素或哌唑嗪的EC20浓度），检查直径对跨壁压力相对于基线的增加和减少的反应。管腔压力增加期间的肌源性收缩和压力降低期间的肌源性抑制在α1-音调期间最大，在内在音调期间较小，在α1-音调期间最小。这些发现表明，局部压力依赖性自动调节机制可能受到α-肾上腺素受体类型和特定组织不同血管段内占主导地位的相对激活的调节。
The interaction of α1- and α2-adrenoceptor constriction of isolated rat cremaster small arteries (mean diameter ± SEM, 114 ± 5 µm) with the myogenic mechanism was examined with in vitro videomicroscopy. Microdissected vessels were double-cannulated with glass micropipets in a tissue bath, and intra-luminal pressure was set at 65 mm Hg baseline pressure. Norepinephrine (NE) concentration-response curves were obtained alone and in the presence of prazosin or rauwolscine to establish the concentrations of NE required to selectively stimulate α1- or α2-adrenoceptors. A bimodal response was produced by NE alone, indicating interaction with more than one receptor population. Rauwolscine and prazosin each produced dextral displacement at low &(<0.1 µM)NE concentrations. However, while prazosin exhibited competitive antagonism, rauwolscine did not antagonize NE at concentrations ≧ EC50value. Thus, both α1and α2-adrenoceptors mediate constriction at low NE concentrations, but only α1-receptors contributed to constriction at intermediate and high concentrations. These data are in contrast to previous findings for the same vessels studied in vivo. Diameter responses to increases and decreases in transmural pressure from baseline were examined in the relaxed (passive) state with nitroprusside present, during spontaneous intrinsic tone, and during induced α1-or α2-tone (EC20concentration of NE plus rauwolscine or prazosin). Myogenic constriction during increases in lumen pressure and myogenic inhibition of tone during decreases in pressure were greatest during α1-tone, less during intrinsic tone and least during α1-tone. These findings suggest that local pressure-dependent autoregulatory mechanisms may be modulated by the type of α-adrenoceptors and relative activation that predominate within the different vascular segments of a particular tissue.