Burson J M, Aguilera G, Gross K W, Sigmund C D
Department of Medicine, University of Iowa College of Medicine, Iowa City 52242.
Am J Physiol. 1994 Aug;267(2 Pt 1):E260-7. doi: 10.1152/ajpendo.1994.267.2.E260.
At least two distinct genes (AT1A and AT1B) encode type 1 angiotensin II (AT1) receptors in rodents. Receptor binding and Northern blot analysis have clearly demonstrated the presence of AT1 receptors and AT1-receptor mRNA in many tissues but fail to differentiate which type 1 receptor subtype is expressed. A reverse-transcriptase polymerase chain reaction restriction fragment length polymorphism (RT-PCR-RFLP) assay was developed to differentiate the expressed mRNA by subtype. Expression of AT1A was clearly evident in kidney, liver, adrenal gland, ovary, brain, testes, adipose tissue, lung, and heart of adult mice. AT1B was absent from most of these tissues but was detectable in brain, testes, and adrenal gland. No significant differences in expression were evident in kidney, liver, brain, lung, or heart from 16.5- or 18.5-gestation-day fetuses, and only AT1A was evident in placenta. Expression of AT1B was confirmed in adrenal gland, brain, and testes, using a primer set that specifically amplifies only AT1B mRNA. Expression of AT1A and AT1B was also examined in As4.1 cells, a renin-expressing mouse kidney tumoral cell line. Receptor binding and competition assays using AT1- and AT2-receptor antagonists revealed that only AT1 receptors are present on the cell surface. Extremely low levels of AT1-receptor mRNA was detected by Northern blot, and RT-PCR-RFLP analysis revealed that only the AT1A subtype is expressed in this cell line. Despite the high homology between the coding sequence of the AT1A and AT1B genes, they exhibit disparate tissue-specific expression profiles.
在啮齿动物中，至少有两个不同的基因（AT1A和AT1B）编码1型血管紧张素II（AT1）受体。受体结合和Northern印迹分析已清楚地证明许多组织中存在AT1受体和AT1受体mRNA，但无法区分表达的是哪种1型受体亚型。开发了一种逆转录酶聚合酶链反应限制性片段长度多态性（RT-PCR-RFLP）检测方法，以按亚型区分表达的mRNA。AT1A在成年小鼠的肾脏、肝脏、肾上腺、卵巢、大脑、睾丸、脂肪组织、肺和心脏中表达明显。这些组织中的大多数都没有AT1B，但在大脑、睾丸和肾上腺中可检测到。在妊娠16.5天或18.5天的胎儿的肾脏、肝脏、大脑、肺或心脏中，表达没有明显差异，并且仅在胎盘中可明显检测到AT1A。使用仅特异性扩增AT1B mRNA的引物对，在肾上腺、大脑和睾丸中证实了AT1B的表达。还在As4.1细胞（一种表达肾素的小鼠肾肿瘤细胞系）中检测了AT1A和AT1B的表达。使用AT1和AT2受体拮抗剂进行的受体结合和竞争试验表明，细胞表面仅存在AT1受体。通过Northern印迹检测到极低水平的AT1受体mRNA，RT-PCR-RFLP分析表明该细胞系中仅表达AT1A亚型。尽管AT1A和AT1B基因的编码序列具有高度同源性，但它们表现出不同的组织特异性表达谱。
