Strum J M, Feldman D, Taggart B, Marver D, Edelman I S
Endocrinology. 1975 Sep;97(3):505-16. doi: 10.1210/endo-97-3-505.
Recently, a class of receptors exhibiting high affinity for corticosterone was described in rat kidney (Feldman, D. et al., Endocrinology 92: 1429, 1973). These receptor sites exhibited negligible affinity for dexamethasone and aldosterone and were designated Type III to distinguish them from sites having high affinity for aldosterone (Type I), and sites with high affinity for dexamethasone and corticosterone (Type II). To visually localize Type III sites in the kidney and demonstrate whether or not they represent intracellular steroid receptors, we used an autoradiographic procedure for diffusible substances. Male adrenalectomized rats were injected intravenously with the following combination of steroids per 100 g body weight: 4 x 10(-9) mol [3H]corticosterone, 4 x 10(-9) mol unlabeled aldosterone, and 4 x 10(-9) mol unlabeled dexamethasone. To differentiate "nonspecific" binding, each experimental animal was paired with a control animal that received the same steroids plus 250-fold unlabeled corticosterone. At 3 min, 10 min, and 30 min, kidneys were removed, cut into quadrants, and frozen in isopentane cooled by liquid nitrogen. For autoradiography, 4 mum frozen sections were cut, pressed into contact with emulsion precoated slides at -30 C, melted and simultaneously dried under a jet of dry nitrogen gas, and exposed at 4 C for 2 to 6 weeks. At all three time intervals, silver grains representing [3H]corticosterone binding sites, were concentrated over collecting tubules, only in the outer medulla and cortex (those in the inner medulla and papilla were not labeled). In the labeled segments of the nephron, some of the cells showed an apparent high ratio of cytoplasmic to nuclear grains and in others nuclear labeling was more prominent. A small population of cells within labeled collecting tubules (possibly dark cells) were not labeled. Although no function can yet be ascribed to Type III receptors in the kidney, they may represent an important steroid-mediated renal mechanism.
最近，在大鼠肾脏中发现了一类对皮质酮具有高亲和力的受体（费尔德曼，D. 等人，《内分泌学》92: 1429, 1973）。这些受体位点对地塞米松和醛固酮的亲和力可忽略不计，被指定为III型，以区别于对醛固酮具有高亲和力的位点（I型）以及对地塞米松和皮质酮具有高亲和力的位点（II型）。为了在肾脏中可视化定位III型位点，并证明它们是否代表细胞内类固醇受体，我们对可扩散物质采用了放射自显影程序。给雄性肾上腺切除的大鼠按每100克体重静脉注射以下类固醇组合：4×10(-9)摩尔[3H]皮质酮、4×10(-9)摩尔未标记的醛固酮和4×10(-9)摩尔未标记的地塞米松。为了区分“非特异性”结合，将每只实验动物与一只对照动物配对，对照动物接受相同的类固醇外加250倍未标记的皮质酮。在3分钟、10分钟和30分钟时，取出肾脏，切成四等份，在液氮冷却的异戊烷中冷冻。用于放射自显影时，切成4微米的冷冻切片，在-30℃下压在预涂有乳剂的载玻片上，在干燥氮气气流下熔化并同时干燥，然后在4℃下曝光2至6周。在所有三个时间间隔，代表[3H]皮质酮结合位点的银颗粒都集中在集合小管上，仅在外髓质和皮质（内髓质和乳头中的未被标记）。在肾单位的标记节段中，一些细胞显示出明显的细胞质与细胞核颗粒高比例，而在其他细胞中细胞核标记更突出。标记的集合小管内一小部分细胞（可能是暗细胞）未被标记。虽然目前还不能赋予肾脏中III型受体任何功能，但它们可能代表一种重要的类固醇介导的肾脏机制。
