Crandall D L, Herzlinger H E, Saunders B D, Armellino D C, Kral J G
Departments of Medicine, SUNY Health Science Center, Brooklyn.
J Lipid Res. 1994 Aug;35(8):1378-85.
Angiotensin II (AII) receptor binding assays were performed in rat adipocytes from three separate anatomic depots. Fat cells were isolated by collagenase digestion, and plasma membranes were prepared from the epididymal, mesenteric, and retroperitoneal fat depots of male Sprague-Dawley rats at 100 days of age. Binding of 125I-labeled [Sar1,Ile8]AII was rapid, saturable, and specific in membranes from all depots, identifying a receptor with a similar affinity of approximately 1 nM. Site-associated differences in receptor number were observed, with epididymal and mesenteric fat cell membranes exhibiting significantly more receptors than retroperitoneal fat cells when binding was expressed per unit of membrane protein. When corrected for cell volume, the number of receptors per cell ranked epididymal > retroperitoneal > mesenteric. Inhibitory constants for the peptide agonists AII and AIII and the peptide antagonist [Sar1,Ala8]AII indicated similar affinities in all three depots. Because the receptor has been classified pharmacologically into two subtypes, the AT1 selective antagonist losartan, and the AT2 selective antagonist PD 123,319 were used to classify the adipocyte receptor, indicating an AT1 subtype with an affinity for losartan in the mesenteric and retroperitoneal adipocytes that was significantly greater than the epididymal. Similar studies were performed in adipocyte membranes obtained from human omental and subcutaneous adipose tissue, revealing the presence of an AII receptor in both depots with an affinity of approximately 10 nM for losartan. These data indicate site-specific differences in AII receptor number in fat cell membranes from rats and the existence of human adipocyte AII receptors, suggesting that the adipocyte is significant for the peripheral metabolism of components of the renin-angiotensin system.
血管紧张素II（AII）受体结合试验在来自三个不同解剖部位的大鼠脂肪细胞中进行。通过胶原酶消化分离脂肪细胞，并从100日龄雄性Sprague-Dawley大鼠的附睾、肠系膜和腹膜后脂肪库制备质膜。125I标记的[Sar1，Ile8]AII在所有脂肪库的膜中的结合都是快速、可饱和且特异的，确定了一种亲和力约为1 nM的受体。观察到受体数量存在部位相关差异，当以每单位膜蛋白表达结合时，附睾和肠系膜脂肪细胞膜显示出比腹膜后脂肪细胞明显更多的受体。校正细胞体积后，每个细胞的受体数量排序为附睾＞腹膜后＞肠系膜。肽激动剂AII和AIII以及肽拮抗剂[Sar1，Ala8]AII的抑制常数表明在所有三个脂肪库中具有相似的亲和力。由于该受体在药理学上已被分为两种亚型，因此使用AT1选择性拮抗剂氯沙坦和AT2选择性拮抗剂PD 123,319对脂肪细胞受体进行分类，表明在肠系膜和腹膜后脂肪细胞中存在对氯沙坦具有亲和力的AT1亚型，其亲和力明显大于附睾脂肪细胞。在从人网膜和皮下脂肪组织获得的脂肪细胞膜中进行了类似的研究，发现在两个脂肪库中均存在AII受体，对氯沙坦的亲和力约为10 nM。这些数据表明大鼠脂肪细胞膜中AII受体数量存在部位特异性差异，并且存在人脂肪细胞AII受体，提示脂肪细胞对肾素-血管紧张素系统成分的外周代谢具有重要意义。
