Meyer C, Christ M, Wehling M
Medizinische Klinik, Klinikum Innenstadt, University of Munich, Germany.
Eur J Biochem. 1995 May 1;229(3):736-40. doi: 10.1111/j.1432-1033.1995.tb20521.x.
Using the radioligand [1,2,6,7-3H]aldosterone ([3H]aldosterone), specific binding sites for aldosterone were identified and characterized in microsomal preparations from porcine liver. The maximum binding capacity is approximately 700 fmol x mg-1 microsomal protein. The reversible binding of [3H]aldosterone was saturable and Scatchard analysis revealed two apparent dissociation constants (Kd), Kd1 < or = 11 nM and Kd2 = 118 nM. Binding was optimal at pH 7.2, thermolabile, and was reduced by more than 70% when membrane vesicles were pretreated with trypsin. Binding was selective for aldosterone with cortisol being a weak agonist at 1000-fold higher concentrations only. Among those detergents tested to optimize conditions for solubilization, n-octylglucoside (75 mM) was most favorable and solubilized 25% of the radioligand-binding protein complex in the undissociated form. These binding sites have unique pharmacological properties, which are similar to those found for aldosterone membrane binding in human lymphocytes and pig kidney, and for rapid aldosterone effects on sodium-proton exchange.
使用放射性配体[1,2,6,7-³H]醛固酮（[³H]醛固酮），在猪肝微粒体制剂中鉴定并表征了醛固酮的特异性结合位点。最大结合容量约为700 fmol x mg⁻¹微粒体蛋白。[³H]醛固酮的可逆结合具有饱和性，Scatchard分析显示两个表观解离常数（Kd），Kd1≤11 nM，Kd2 = 118 nM。结合在pH 7.2时最佳，对热不稳定，并且当膜囊泡用胰蛋白酶预处理时结合减少超过70%。结合对醛固酮具有选择性，皮质醇仅在浓度高1000倍时为弱激动剂。在测试以优化溶解条件的那些去污剂中，正辛基葡糖苷（75 mM）最有利，并且以未解离形式溶解了25%的放射性配体结合蛋白复合物。这些结合位点具有独特的药理学特性，与在人淋巴细胞和猪肾中发现的醛固酮膜结合以及醛固酮对钠-质子交换的快速作用的特性相似。
