Behrens C M, Ramachandran J
Biochim Biophys Acta. 1981 Feb 5;672(3):268-79. doi: 10.1016/0304-4165(81)90293-2.
A specific and sensitive assay for determining the binding of adrenocorticotropin (ACTH) to isolated rat adipocytes has been developed and utilized to study the effect of glucocorticoids on ACTH receptor. Measurement of the binding of tritiated ACTH (spec. act. 90 Ci/mmol) to adipocytes isolated from normal, adrenalectomized, and adrenalectomized dexamethasone-treated rats indicated that there are no differences among these three populations in either the magnitude or the affinity of the binding reaction. The binding interaction was found to be of high affinity (Kd = 5.23 + 1.92 . 10(-9) M and paralleled closely the stimulation of lipolysis (Km = 2.09 +/- 0.35 . 10(-9) M. About 16,300 receptors were calculated to be presented per adipocyte. Hormone-induced cyclic 3',5'-adenosine monophosphate production remained intact after adrenalectomy, thereby confirming that receptors are not lost during steroid deprivation. The lipolytic response did, however, become less sensitive to both ACTH and epinephrine following adrenalectomy. Pre-treatment of adrenalectomized rats with dexamethasone resulted in an increase in basal and hormone-stimulated levels of cyclic AMP and glycerol production to super-normal values. In adipocyte ghost preparations, ACTH and epinephrine sensitive adenylate cyclase activity was not decreased by adrenalectomy and dexamethasone administration did not result in a selective enhancement of ACTH sensitive adenylate cyclase activity. Our results indicate that glucocorticoids do not cause their permissive effects by specific regulation of the ACTH receptor on the adipocyte.
已开发出一种特异性和敏感性高的检测方法，用于测定促肾上腺皮质激素（ACTH）与分离的大鼠脂肪细胞的结合，并用于研究糖皮质激素对ACTH受体的影响。测量氚标记的ACTH（比活度90 Ci/mmol）与从正常、肾上腺切除和肾上腺切除后用 dexamethasone 处理的大鼠分离的脂肪细胞的结合，结果表明这三组细胞在结合反应的强度或亲和力方面均无差异。发现结合相互作用具有高亲和力（Kd = 5.23 + 1.92. 10(-9) M），并且与脂肪分解的刺激密切平行（Km = 2.09 +/- 0.35. 10(-9) M）。计算得出每个脂肪细胞约有16,300个受体。肾上腺切除后，激素诱导的环3',5'-腺苷单磷酸生成保持完整，从而证实受体在类固醇剥夺期间不会丢失。然而，肾上腺切除后，脂肪分解反应对ACTH和肾上腺素的敏感性确实降低。用dexamethasone预处理肾上腺切除的大鼠，导致基础和激素刺激的环磷酸腺苷水平以及甘油生成增加至超正常水平。在脂肪细胞膜空壳制剂中，肾上腺切除并未降低ACTH和肾上腺素敏感的腺苷酸环化酶活性，dexamethasone给药也未导致ACTH敏感的腺苷酸环化酶活性选择性增强。我们的结果表明，糖皮质激素不会通过对脂肪细胞上ACTH受体的特异性调节来产生其允许作用。
