Uehara A
Hokkaido Igaku Zasshi. 1985 May;60(3):375-90.
The changes in glucagon receptors of white adipocytes from cold-acclimated rats were investigated to know the metabolic role of glucagon in cold acclimation by establishing a glucagon radioreceptor assay system for isolated white adipocytes. Glucagon radioreceptor assay methodology The binding of 125I-labelled glucagon to isolated epididymal white adipocytes was linearly related to the number of cells (0.5-2.0 X 10(5) cells/ml) added in the medium. At a cell concentration higher than 3.0 X 10(5) cells/ml, the amount of specific binding failed to show the proportional relationship to the number of adipocytes. The effects of incubation temperature (4 degrees C, 25 degrees C and 37 degrees C) on the glucagon binding were investigated. Incubation at 25 degrees C was adopted in the present study because of the highest maximum binding and the longest steady state obtained. Preincubation at 25 degrees C for 15 min increased significantly the amount of specific binding. It was confirmed that bacitracin, polypeptide antibiotics, inhibited significantly the degradation of glucagon. The glucagon binding under these conditions was found to be saturable and reversible, validating a specific reaction for the glucagon receptor. When a Scatchard plot was constructed, the data was curvilinear with an upward concavity, indicating the presence of at least two classes of binding site with different fixed affinities or of negatively cooperative interactions between receptors. It was concluded that an appropriate condition for glucagon receptor assay of white adipocytes consists of cell concentration of 1 X 10(5) cells/ml, 15 minute-preincubation and 30 minute-reaction at 25 degrees C in the presence of bacitracin (1 mg/ml). Effect of cold acclimation on glucagon receptors of white adipocytes Cold acclimation decreased the size and increased the number of epididymal white adipocytes. Cold acclimation increased the number of glucagon receptors of white adipocytes; about 140% increase expressed as per cell, approximately 260% increase per unit of surface area and 210% increase per whole tissue. The affinity of binding sites was not changed. The increased binding sites could explain, at least partly, the enhanced metabolic response of cold-acclimated rats to glucagon.
通过建立分离的白色脂肪细胞的胰高血糖素放射受体分析系统，研究冷适应大鼠白色脂肪细胞中胰高血糖素受体的变化，以了解胰高血糖素在冷适应中的代谢作用。
胰高血糖素放射受体分析方法
125I标记的胰高血糖素与分离的附睾白色脂肪细胞的结合与培养基中添加的细胞数量（0.5 - 2.0×10(5)个细胞/ml）呈线性关系。当细胞浓度高于3.0×10(5)个细胞/ml时，特异性结合量与脂肪细胞数量未呈现比例关系。研究了孵育温度（4℃、25℃和37℃）对胰高血糖素结合的影响。本研究采用25℃孵育，因为在此温度下最大结合量最高且达到稳态的时间最长。在25℃预孵育15分钟可显著增加特异性结合量。已证实杆菌肽（一种多肽抗生素）可显著抑制胰高血糖素的降解。发现在这些条件下胰高血糖素的结合是可饱和且可逆的，证实了胰高血糖素受体的特异性反应。构建Scatchard图时，数据呈向上凹陷的曲线，表明存在至少两类具有不同固定亲和力的结合位点或受体之间存在负协同相互作用。得出结论，白色脂肪细胞胰高血糖素受体分析的适宜条件为：细胞浓度1×10(5)个细胞/ml，在25℃下预孵育15分钟、反应30分钟，同时存在杆菌肽（1mg/ml）。
冷适应对白色脂肪细胞胰高血糖素受体的影响
冷适应使附睾白色脂肪细胞体积减小但数量增加。冷适应增加了白色脂肪细胞中胰高血糖素受体的数量；以每个细胞计算增加约140%，以单位表面积计算约增加260%，以整个组织计算约增加210%。结合位点的亲和力未改变。增加的结合位点至少可部分解释冷适应大鼠对胰高血糖素代谢反应增强的现象。
