Feuillan P P, Millan M A, Aguilera G
Section on Endocrine Physiology, National Institute of Child Health and Human Development, NIH, Bethesda, MD 20892.
Regul Pept. 1993 Mar 19;44(2):159-69. doi: 10.1016/0167-0115(93)90239-5.
Angiotensin II (AII) receptor subtypes were studied in the 18-day gestation fetal rat, using two non-peptide AII antagonists: (2-n-butyl-4-chloro-5-hydroxymethyl-1-(2'-(1H-tetrazol-5-yl) biphenyl-4-yl)methyl)imidazol (DuP 753; type 1 (AT1) specific), and 1-(4-amino-3-methylphenyl)methyl-5-diphenacetyl -4,5,6,7-tetrahydro-1-H-imidazo[4,5-c]pyridine-6-carboxylic acid (PD 123177; type 2 (AT2) specific). Autoradiography using 125I(-)[Sar1,Ile8]AII showed that 10 microM PD 123177 decreased binding to near-nonspecific levels in skin, skeletal muscle and adrenal medulla, whereas 10 microM DuP 753 blocked binding in the liver and lung. Studies in skin and liver membranes confirmed the autoradiographic data: AT1 receptors were predominant in the liver (95%), and AT2 in the skin (97%). There was no cross-reactivity between receptor subtype and the heterologous antagonist up to a concentration of 10 microM. In both skin and liver, 2 mM dithiothreitol enhanced the binding of AT2 receptors by increasing receptor affinity, but inhibited binding of AT1 by decreasing the receptor number. In the absence of antagonists, guanyl nucleotides, added at equilibrium, caused marked dissociation of 125I-AII binding in liver membranes, but had minimal effect in skin. However, dissociation occurred in the skin when AT2 sites were blocked with 10 microM PD 123177, and in liver, dissociation was not observed when AT1 sites were blocked with DuP 753. Hence, in contrast to classical AII target tissues, which contain predominantly AT1, most of the sites in fetal skin and skeletal muscle are AT2. The demonstration that the effects of guanyl nucleotides are selective for receptor subtype suggests that the AT1 receptor, but not the AT2, is coupled to cell function via guanyl nucleotide binding proteins. The functional importance of the AT2 receptors and their role in fetal physiology is under current investigation.
使用两种非肽类血管紧张素II（AII）拮抗剂，对妊娠18天的胎鼠体内的AII受体亚型进行了研究：（2 - 正丁基 - 4 - 氯 - 5 - 羟甲基 - 1 - （2'-（1H - 四氮唑 - 5 - 基）联苯 - 4 - 基）甲基）咪唑（DuP 753；对1型（AT1）受体具有特异性），以及1 - （4 - 氨基 - 3 - 甲基苯基）甲基 - 5 - 二苯乙酰基 - 4,5,6,7 - 四氢 - 1 - H - 咪唑并[4,5 - c]吡啶 - 6 - 羧酸（PD 123177；对2型（AT2）受体具有特异性）。使用125I（-）[Sar1，Ile8]AII进行放射自显影显示，10微摩尔的PD 123177可使皮肤、骨骼肌和肾上腺髓质中的结合减少至接近非特异性水平，而10微摩尔的DuP 753可阻断肝脏和肺中的结合。对皮肤和肝脏膜的研究证实了放射自显影数据：AT1受体在肝脏中占主导地位（95%），而AT2受体在皮肤中占主导地位（97%）。在浓度高达10微摩尔时，受体亚型与异源拮抗剂之间没有交叉反应。在皮肤和肝脏中，2毫摩尔的二硫苏糖醇通过增加受体亲和力增强了AT2受体的结合，但通过减少受体数量抑制了AT1受体的结合。在没有拮抗剂的情况下，在平衡时添加的鸟苷酸会导致肝脏膜中125I - AII结合的明显解离，但对皮肤的影响最小。然而，当用10微摩尔的PD 123177阻断AT2位点时，皮肤中会发生解离，而在用DuP 753阻断AT1位点时，肝脏中未观察到解离。因此，与主要含有AT1的经典AII靶组织不同，胎儿皮肤和骨骼肌中的大多数位点是AT2。鸟苷酸的作用对受体亚型具有选择性这一证明表明，AT1受体而非AT2受体是通过鸟苷酸结合蛋白与细胞功能偶联的。AT2受体的功能重要性及其在胎儿生理学中的作用目前正在研究中。
