Quelle F W, Smith R V, Hrycyna C A, Kaliban T D, Crooks J A, O'Brien J M
Department of Chemistry and Biochemistry, Middlebury College, Vermont 05753.
Endocrinology. 1988 Sep;123(3):1642-51. doi: 10.1210/endo-123-3-1642.
Using liver from nonadrenalectomized adult male rats, binding sites for [3H]dexamethasone in particulate fractions are demonstrated. The binding is thermolabile, saturable, and specific for glucocorticoid. The apparent dissociation constant (Kdapp) for [3H]dexamethasone (0.48 +/- 0.084 microM) is 60-fold greater than that for cytosolic receptor (7.9 +/- 1.5 nM). The Kdapp for [3H]cortisol in particulate fractions is 2.5-fold lower than for [3H]dexamethasone (Kdapp = 0.18 microM). The binding capacities for particulate and cytosolic glucocorticoid-binding sites also differ significantly, with particulate sites at least 9.1-fold more concentrated than cytosolic sites in liver tissue. Particulate sites are determined in Percoll density gradients to have a density of 1.039 g/cc. Saturable [3H]dexamethasone radioactivity coelutes from these gradients with the plasma membrane marker enzyme 5'-nucleotidase. Adrenalectomy causes the complete loss of particulate binding sites by 6 days postadrenalectomy; however, these sites can be regenerated to two thirds of the nonadrenalectomy level by 20-30 days postadrenalectomy.
利用未切除肾上腺的成年雄性大鼠的肝脏，证明了微粒体部分存在[3H]地塞米松结合位点。这种结合对温度敏感、具有饱和性且对糖皮质激素具有特异性。[3H]地塞米松的表观解离常数（Kdapp）为（0.48±0.084微摩尔），比胞质受体的解离常数（7.9±1.5纳摩尔）大60倍。微粒体部分[3H]皮质醇的Kdapp比[3H]地塞米松低2.5倍（Kdapp = 0.18微摩尔）。微粒体和胞质糖皮质激素结合位点的结合容量也有显著差异，肝脏组织中微粒体位点的浓度至少比胞质位点高9.1倍。在Percoll密度梯度中测定微粒体位点的密度为1.039克/立方厘米。可饱和的[3H]地塞米松放射性与质膜标记酶5'-核苷酸酶从这些梯度中共洗脱。肾上腺切除术后6天，微粒体结合位点完全丧失；然而，肾上腺切除术后20 - 30天，这些位点可恢复到未切除肾上腺水平的三分之二。
