Link R P, DeLuca H F
Genex Corporation, Gaithersburg, MD 20877.
Steroids. 1988 May-Jun;51(5-6):583-98. doi: 10.1016/0039-128x(88)90054-2.
The binding activity of four vitamin D metabolites and/or analogs for the intestinal 1,25-dihydroxyvitamin D3 receptor was evaluated after incubation at 25 degrees C for 1 h or at 0-4 degrees C for 18 h. The incubation conditions, which had no effect on the binding of 1,25-dihydroxyvitamin D3, had a dramatic effect on the binding of 25-hydroxyvitamin D3 and 1 alpha-hydroxyvitamin D3 and a small but reproducible effect on 24,25-dihydroxyvitamin D3 binding to receptor. Affinities 10- to 20-fold higher were obtained for 25-hydroxyvitamin D3 and 1 alpha-hydroxyvitamin D3, and affinities 3-fold higher were obtained for 24,25-dihydroxyvitamin D3 at the 0-4 degrees C/18-h incubation. A comparison of intestinal receptor from chick and pig with nine vitamin D compounds showed no major differences between the two species. The relative affinity of the vitamin D analogs to compete with tritiated 1,25-dihydroxyvitamin D3 for the receptor in pig nuclear extract, expressed as ratios of the molar concentration required for 50% binding of the tritiated 1,25-dihydroxyvitamin D3 compared to nonradioactive 1,25-dihydroxyvitamin D3, are as follows: 1,25-dihydroxyvitamin D3 (1) = 1,25-dihydroxyvitamin D2 = 24-homo-1,25-dihydroxyvitamin D3 greater than 1,24,25-trihydroxyvitamin D3 (4) greater than 25-hydroxyvitamin D3 (21) = 10-oxo-19-nor-25-hydroxyvitamin D3 = 1 alpha-hydroxyvitamin D3 (37) greater than 24,25-dihydroxyvitamin D2 (257) much much greater than vitamin D3 (greater than 10(6)).
在25℃孵育1小时或在0-4℃孵育18小时后，评估了四种维生素D代谢物和/或类似物对肠道1,25-二羟基维生素D3受体的结合活性。这些孵育条件对1,25-二羟基维生素D3的结合没有影响，但对25-羟基维生素D3和1α-羟基维生素D3的结合有显著影响，对24,25-二羟基维生素D3与受体的结合有微小但可重复的影响。在0-4℃/18小时孵育时，25-羟基维生素D3和1α-羟基维生素D3的亲和力提高了10至20倍，24,25-二羟基维生素D3的亲和力提高了3倍。对鸡和猪的肠道受体与九种维生素D化合物进行比较，结果显示这两个物种之间没有主要差异。维生素D类似物与猪核提取物中受体上的氚标记1,25-二羟基维生素D3竞争的相对亲和力，以氚标记的1,25-二羟基维生素D3与非放射性1,25-二羟基维生素D3 50%结合所需的摩尔浓度之比表示，如下：1,25-二羟基维生素D3(1)=1,25-二羟基维生素D2=24-同型-1,25-二羟基维生素D3＞1,24,25-三羟基维生素D3(4)＞25-羟基维生素D3(21)=10-氧代-19-去甲-25-羟基维生素D3=1α-羟基维生素D3(37)＞24,25-二羟基维生素D2(257)＞＞维生素D3(＞10⁶)。
