Oelofsen W, Ramachandran J
Arch Biochem Biophys. 1983 Sep;225(2):414-21. doi: 10.1016/0003-9861(83)90048-6.
Synthetic [125I]-Tyr23, Phe2, Nle4-adrenocorticotropin (ACTH)-(1-38) [( 125I]-ACTH analog) with full biological potency and near theoretical specific radioactivity (1800 +/- 75 Ci/mmol) was used to investigate ACTH receptors on isolated rat adipocytes derived from 42-day-old rats. Binding to adipocytes was studied in the presence of 1% bovine serum albumin (BSA) as well as 4% BSA. The interaction of the [125I]-ACTH analog with adipocytes was highly specific, rapid, saturable, and reversible. Scatchard analysis of the binding data obtained in medium containing 1% BSA revealed a single class of binding sites with an apparent KD = 170 +/- 11.9 pM. Competition experiments with unlabeled ACTH also yielded a comparable value for the apparent KD (143 +/- 16.5 pM). The number of receptors per adipocyte was quite low (521-841/cell). The stimulation of lipolysis by ACTH was closely correlated with the binding, the apparent Km being 145-177 pM. At a concentration of 4% BSA in the incubation medium, the binding curve was shifted significantly to the right (apparent KD = 446 +/- 77 pM) and the binding capacity was also significantly enhanced (1663 +/- 208/cell) without any change in the apparent Km for glycerol release (187 +/- 7.1 pM).
具有完全生物活性和接近理论比放射性（1800±75居里/毫摩尔）的合成[125I]-酪氨酸23、苯丙氨酸2、亮氨酸4-促肾上腺皮质激素（ACTH）-（1-38）[（125I]-ACTH类似物）被用于研究源自42日龄大鼠的分离大鼠脂肪细胞上的ACTH受体。在1%牛血清白蛋白（BSA）以及4% BSA存在的情况下研究了与脂肪细胞的结合。[125I]-ACTH类似物与脂肪细胞的相互作用具有高度特异性、快速、可饱和且可逆。对在含有1% BSA的培养基中获得的结合数据进行Scatchard分析，揭示了一类单一的结合位点，其表观解离常数KD = 170±11.9皮摩尔。用未标记的ACTH进行的竞争实验也得出了类似的表观KD值（143±16.5皮摩尔）。每个脂肪细胞的受体数量相当低（521 - 841/细胞）。ACTH对脂肪分解的刺激与结合密切相关，表观米氏常数为145 - 177皮摩尔。在孵育培养基中BSA浓度为4%时，结合曲线明显右移（表观KD = 446±77皮摩尔），结合能力也显著增强（1663±208/细胞），而甘油释放的表观米氏常数没有任何变化（187±7.1皮摩尔）。
