Tissue Specificity of Endothelin Binding Sites
Tissue Specificity of Endothelin Binding Sites
复制标题
内皮素结合位点的组织特异性
DOI：
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发表时间：
1990
影响因子：
3
通讯作者：
J. Jaramillo
中科院分区：
文献类型：
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作者：
G. Bolger;F. Liard;R. Krogsrud;D. Thibeault;J. Jaramillo
测定了125i标记内皮素（125I-ET）与大鼠主动脉、心房、心室、门静脉、气管、肺实质、输精管、回肠、膀胱、豚鼠大肠带绦虫和肺实质粗膜组分的结合情况。所有组织中125I-ET结合的Scatchard分析表明，125I-ET只与一类饱和位点结合。125I-ET结合位点的亲和力和密度在不同组织间存在差异。125I-ET对大鼠主动脉、气管、肺实质、脑室、膀胱、输精管、豚鼠大肠带绦虫及肺实质的结合Kd≤0.5 nM，对大鼠门静脉、心房的结合Kd≤1.8 nM，对回肠的结合Kd≤3.3 nM。125I-ET在大鼠组织中的Bmax密度大小顺序为：气管>肺实质=输精管±主动脉=门静脉=心房>膀胱>脑室=回肠。研究了125I-ET内皮素在大鼠脑室膜上的结合特性。125I-ET的结合与时间有关，在25°C下45-60 min内达到最大值。计算得到的微关联常数为9.67±105 s−1 M−1。只有15-20%的125I-ET从其结合位点解离，即使研究解离时间长达3小时。用ET预孵生脑室膜可阻止125I-ET的结合。125I-ET的结合被脑室膜的沸腾破坏，并且依赖于温度、pH和阳离子（Ca2+、Mg2+和Na+）。F125I-ET的结合不受特定钙通道配体、n -甲基- d -天冬氨酸（NMDA）受体控制的离子通道拮抗剂、外周苯二氮卓类药物、阿片类药物、心房利钠因子、血管紧张素II和硝普钠的影响。在大鼠和豚鼠组织中，ET结合位点的密度与ET的收缩效能之间没有相关性。体外将大鼠心房组织暴露于ET （10 - 7 M）中，可显著（25%）抑制ET与从这些组织分离的心房膜的结合。这些结果表明，在许多组织中存在不同性质的特异性高亲和力125I-ET结合位点。ET结合不表现出简单的可逆双分子动力学，而是表现出不可逆结合的动力学特征。
A measurement was made of the binding of 125I-labeled endothelin (125I-ET) to crude membrane fractions prepared from rat aorta, atrium, ventricle, portal vein, trachea, lung parenchyma, vas deferens, ileum, bladder, and guinea-pig taenia coli and lung parenchyma. Scatchard analysis of 125I-ET binding in all tissues indicated binding to a single class of saturable sites. The affinity and density of 125I-ET binding sites varied between tissues. The Kd of 125I-ET binding was ≤0.5 nM for rat aorta, trachea, lung parenchyma, ventricle, bladder, and vas deferens, and guinea-pig taenia coli and lung parenchyma, 1.8 nM for rat portal vein and atrium, and 3.3 nM for ileum. The Bmax of 125I-ET binding had the following rank order of density in rat tissues: trachea > lung parenchyma = vas deferens ± aorta = portal vein = atrium > bladder > ventricle = ileum. The properties of 125I-ET endothelin binding were characterized in rat ventricular membranes. 125I-ET binding was time dependent, reaching a maximum within 45–60 min at 25°C. The calculated microassociation constant was 9.67 ± 105 s−1 M−1. Only 15–20% of 125I-ET dissociated from its binding site even when dissociation was studied as long as 3 h. Preincubation of ventricular membranes with ET prevented binding of 125I-ET. 125I-ET binding was destroyed by boiling of ventricular membranes and was temperature, pH, and cation (Ca2+, Mg2+, and Na+) dependent. F125I-ET binding was not affected by specific calcium channel ligands, N-methyl-D-aspartate (NMDA) receptor-gated ionophore antagonists, peripheral benzodiazepines, opiates, atrial natriuretic factor, angiotensin II, and sodium nitroprusside. There was no correlation between the density of ET binding sites and the contractile efficacy of ET in rat and guinea pig tissues. Exposure of rat atrium tissues to ET (10−7 M) in vitro resulted in a significant (25%) inhibition of ET binding to atrium membranes isolated from these tissues. These results indicate that specific high-affinity 125I-ET binding sites with varying properties exist in a number of tissues. ET binding does not display simple reversible bimolecular kinetics but instead demonstrates kinetics characteristic of irreversible binding.