DeLuca H F, Nakada M, Tanaka Y, Sicinski R, Phelps M
Department of Biochemistry, College of Agricultural and Life Sciences, University of Wisconsin-Madison 53706.
Biochim Biophys Acta. 1988 Apr 14;965(1):16-21. doi: 10.1016/0304-4165(88)90145-6.
The binding of 25-hydroxy-[26,27-3H]vitamin D-3 and 25-hydroxy-[26,27-3H]vitamin D-2 to the vitamin D binding protein in the plasma of both rats and chicks has been studied. In the case of rats, sucrose density gradient analysis, competitive displacement, and Scatchard analysis demonstrate that 25-hydroxyvitamin D-3 and 25-hydroxyvitamin D-2 are bound equally well to the vitamin D binding protein. In contrast, 25-hydroxyvitamin D-2 is poorly bound, while 25-hydroxyvitamin D-3 is tightly bound to the vitamin D binding protein in chick plasma. On the other hand, the chick intestinal receptor binds 1,25-dihydroxyvitamin D-2 and 1,25-dihydroxyvitamin D-3 equally well with a KD of 7.10(-11) M for both compounds. These results strongly suggest that the failure of the plasma transport protein in chicks to bind the vitamin D-2 compounds may be responsible for their relative ineffectiveness in these animals.
对大鼠和雏鸡血浆中维生素D结合蛋白与25-羟基-[26,27-³H]维生素D-3及25-羟基-[26,27-³H]维生素D-2的结合情况进行了研究。就大鼠而言，蔗糖密度梯度分析、竞争性置换分析和斯卡查德分析表明，25-羟基维生素D-3和25-羟基维生素D-2与维生素D结合蛋白的结合情况同样良好。相比之下，在雏鸡血浆中，25-羟基维生素D-2结合较差，而25-羟基维生素D-3与维生素D结合蛋白紧密结合。另一方面，雏鸡肠道受体对1,25-二羟基维生素D-2和1,25-二羟基维生素D-3的结合情况同样良好，两种化合物的解离常数KD均为7×10⁻¹¹ M。这些结果有力地表明，雏鸡血浆转运蛋白无法结合维生素D-2化合物可能是其在这些动物体内相对无效的原因。
