QUANTITATIVE AUTORADIOGRAPHY OF ANGIOTENSIN-II AT(2), RECEPTORS WITH [I-125] CGP 42112
QUANTITATIVE AUTORADIOGRAPHY OF ANGIOTENSIN-II AT(2), RECEPTORS WITH [I-125] CGP 42112
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DOI：
10.1016/0006-8993(95)00092-5
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发表时间：
1995-04-17
期刊：
影响因子：
2.9
通讯作者：
SAAVEDRA, JM
中科院分区：
文献类型：
--
作者：
HEEMSKERK, FMJ;SAAVEDRA, JM
大多数血管紧张素II（Ang II）受体的放射性标记配体不能区分AT（1）和AT（2）受体亚型，必须通过选择性AT（1）或AT（2）配体的置换来区分。我们比较了[I-125]CGP 42112与非选择性激动剂[I-125]Sar（1）血管紧张素II。我们用定量放射自显影和膜结合技术研究了下橄榄核、内侧膝状体核和肾上腺髓质富含AT（2）受体的区域。[I-125]CGP 42112以高亲和力结合（Kd = 0.07-0.3 nM，取决于研究区域）。[I-125]CGP 42112与AT（2）受体的结合具有选择性，这是通过与AT（1）配体氯沙坦缺乏竞争以及与AT（2）配体PD 123177和未标记的CGP 42112以及非选择性肽Ang II和血管紧张素III（Ang III）的竞争确定的。使用[I-125]CGP 42112结合，我们发现使用定量放射自显影或膜结合方法的效力顺序相同：CGP 42112 > Ang II = Ang III > PD 123177。我们的研究结果表明，[I-125]CGP 42112是AT（2）受体最具选择性、最高亲和力的配体。由于这些特性和低非特异性结合，[I-125]CGp 42112的定量放射自显影是选择性表征AT（2）受体的首选方法，尤其是在受体亚型分布高度不均匀的组织（如脑）中。
Most radiolabeled ligands for angiotensin II (Ang II) receptors do not discriminate between the AT(1) and AT(2) receptor subtypes, which must be distinguished by displacement with selective AT(1) or AT(2) ligands. We compared [I-125]CGP 42112 with the non-selective agonist [I-125]Sar(1)Angiotensin II. We studied the inferior olive, medial geniculate nucleus and the adrenal medulla, areas rich in AT(2) receptors, using both ligands with quantitative autoradiography and membrane binding techniques. [I-125]CGP 42112 bound with high affinity (K-d = 0.07-0.3 nM, depending on the area studied). [I-125]CGP 42112 binding was selective for AT(2) receptors, as determined by lack of competition with the AT(1) ligand losartan, and competition by the AT(2) ligands PD 123177 and unlabeled CGP 42112 and the non-selective peptides Ang II and angiotensin III (Ang III). Using [I-125]CGP 42112 binding, we found the same order of potency: CGP 42112 > Ang II = Ang III > PD 123177 using both quantitative autoradiography or membrane binding methods. Our results demonstrate that [I-125]CGP 42112 is the most selective, highest affinity ligand available for AT(2) receptors. Because of these characteristics, and low non-specific binding, quantitative autoradiography with [I-125]CGp 42112 is the method of choice to selectively characterize AT(2) receptors, especially in tissues like the brain, with a highly heterogeneous distribution of receptor subtypes.