DiBattista J A, Mehdi A Z, Sandor T
Gen Comp Endocrinol. 1985 Jul;59(1):31-49. doi: 10.1016/0016-6480(85)90416-2.
The corticosteroid receptor profile of the intestinal tract of the domestic duck (maintained on either a low-sodium (LS) or a high-sodium (HS) diet) was investigated. Using tritiated triamcinolone acetonide (TA), corticosterone, or aldosterone as ligands, cytoplasmic mineralocorticoid receptors (MR, type I) and glucocorticoid receptors (GR, type II) were found in the mucosal cytosol of the jejunum and colon with the following binding parameters: LS jejunum GR-Kd, 3.4 nM; Nmax, 245 fmol/mg protein; MR-Kd, 0.54 nM; Nmax, 35 fmol/ mg protein; colon GR-3.2 nM; Nmax, 531 fmol/mg protein; MR-Kd, 0.55 nM; Nmax, 113 fmol/mg protein; HS jejunum GR--Kd, 3.2 nM; Nmax, 531 fmol/mg protein; MR--Kd, 0.30 nM; Nmax, 50 fmol/mg protein; colon GR--Kd, 1.1 nM; Nmax, 572 fmol/mg protein; MR--Kd, 0.68 nM; Nmax, 221 fmol/mg protein. The diet little influenced the GR binding parameters, while the MR (aldosterone) binding parameters showed a down-regulation following LS (high circulating aldosterone) diets. The competition hierarchy of radioinert steroids on the formation of the [3H]corticosterone-receptor complex was corticosterone = cortisol = 11-deoxycorticosterone greater than aldosterone = TA = dexamethasone much greater than 11-deoxycortisol; with [3H]aldosterone, the competition was corticosterone = progesterone = 11-deoxycorticosterone greater than aldosterone = cortisol = TA = dexamethasone greater than 11-deoxycortisol greater than 11-dehydrocorticosterone. The intestinal mucosal receptor was deactivated following treatment with trypsin. On linear sucrose gradients, receptor-ligand complexes sedimented with a single peak at 8.5 S (hypotonic gradient) and 4.0-4.5 S (hypertonic gradient), respectively. Heat-activated [3H]TA- and [3H]aldosterone-receptor complexes bound avidly to DNA-cellulose and, upon ion-exchange chromatography on DEAE-Sephacel, the presence of the negatively charged unactivated and the more positively charged activated complexes could be shown. The hydrodynamic parameters, determined by gel-filtration chromatography, gave for all three ligand-receptor complexes molecular weight values from 334,000 to 351,000 and Stokes radii from 76.8 to 80.0 A. From these studies it was concluded that the duck intestinal tract possesses vertebrate-type GR and MR, though these receptors were much less specific than their mammalian counterparts. The duck intestinal corticosteroid receptor was found to be different from those of the teleost fish and anuran amphibian, establishing the possibility of a biochemical evolution in nonmammalian intestinal corticosteroid receptor conformation.
研究了家鸭（分别饲喂低钠（LS）或高钠（HS）日粮）肠道的皮质类固醇受体特征。以氚化曲安奈德（TA）、皮质酮或醛固酮作为配体，在空肠和结肠的黏膜胞质溶胶中发现了细胞质盐皮质激素受体（MR，I型）和糖皮质激素受体（GR，II型），其结合参数如下：LS空肠GR-Kd为3.4 nM；Nmax为245 fmol/mg蛋白质；MR-Kd为0.54 nM；Nmax为35 fmol/mg蛋白质；结肠GR为3.2 nM；Nmax为531 fmol/mg蛋白质；MR-Kd为0.55 nM；Nmax为113 fmol/mg蛋白质；HS空肠GR-Kd为3.2 nM；Nmax为531 fmol/mg蛋白质；MR-Kd为0.30 nM；Nmax为50 fmol/mg蛋白质；结肠GR-Kd为1.1 nM；Nmax为572 fmol/mg蛋白质；MR-Kd为0.68 nM；Nmax为221 fmol/mg蛋白质。日粮对GR结合参数影响不大，而MR（醛固酮）结合参数在LS（循环醛固酮水平高）日粮后出现下调。放射性惰性类固醇对[3H]皮质酮-受体复合物形成的竞争顺序为皮质酮 = 皮质醇 = 11-脱氧皮质酮＞醛固酮 = TA = 地塞米松＞＞11-脱氧皮质醇；对于[3H]醛固酮，竞争顺序为皮质酮 = 孕酮 = 11-脱氧皮质酮＞醛固酮 = 皮质醇 = TA = 地塞米松＞11-脱氧皮质醇＞11-脱氢皮质酮。用胰蛋白酶处理后，肠道黏膜受体失活。在线性蔗糖梯度上，受体-配体复合物分别在8.5 S（低渗梯度）和4.0 - 4.5 S（高渗梯度）处有一个单一峰沉降。热激活的[3H]TA-和[3H]醛固酮-受体复合物能与DNA-纤维素紧密结合，在DEAE-琼脂糖离子交换色谱上，可以显示出带负电荷的未激活复合物和带更多正电荷的激活复合物的存在。通过凝胶过滤色谱法测定的流体动力学参数表明，所有三种配体-受体复合物的分子量值在334,000至351,000之间，斯托克斯半径在76.8至80.0 Å之间。从这些研究得出结论：鸭肠道具有脊椎动物类型的GR和MR，尽管这些受体的特异性远低于其哺乳动物对应物。发现鸭肠道皮质类固醇受体与硬骨鱼和无尾两栖动物的不同，这表明非哺乳动物肠道皮质类固醇受体构象可能存在生化进化。
