Shultz T D, Fox J, Heath H, Kumar R
Proc Natl Acad Sci U S A. 1983 Mar;80(6):1746-50. doi: 10.1073/pnas.80.6.1746.
Recent experiments have shown that 1,25-dihydroxyvitamin D3-like material is produced in cultured nonrenal cells and may be present in the sera of anephric patients. We reexamined the question of whether 1,25-dihydroxyvitamin D3 can be synthesized extrarenally in the rat in vivo. To intact, sham-operated, ureter-ligated, or acutely nephrectomized vitamin D-deficient rats raised on a diet normal in calcium and phosphorus, we gave a physiologic dose of high-specific-activity 25-hydroxy-[3H]vitamin D3 (3.6-3.8 microCi; approximately equal to 25 pmol per rat). Twenty-four hours later we examined their tissues and plasma for the presence of radiolabeled 1,25-dihydroxyvitamin D3. Large amounts of radioactivity that behaved chromatographically as identical with authentic 1,25-dihydroxyvitamin D3 were present in the plasma, bone, and intestine of the intact, sham-operated, or ureter-ligated rats. However, no radioactivity eluting in a manner similar to 1,25-dihydroxyvitamin D3 was found in plasma, bone, or intestine of acutely nephrectomized rats. We conclude that, in the acutely nephrectomized living rat, 1,25-dihydroxyvitamin D3 is not present in plasma, bone, or intestine in quantities detectable by the sensitive techniques we have used. No conversion of 25-hydroxyvitamin D3 to 1,25-dihydroxyvitamin D3 was observed during a 24-hr period after nephrectomy of vitamin D-deprived rats. This fact casts doubt upon the significance of the in vitro production of 1,25-dihydroxyvitamin D3 by nonrenal cells as an in vivo phenomenon.
最近的实验表明，1,25 - 二羟维生素D3样物质可在培养的非肾细胞中产生，且可能存在于无肾患者的血清中。我们重新研究了1,25 - 二羟维生素D3是否能在大鼠体内肾外合成这一问题。对于以钙和磷含量正常的饮食饲养的维生素D缺乏的完整大鼠、假手术大鼠、输尿管结扎大鼠或急性肾切除大鼠，我们给予生理剂量的高比活度25 - 羟 - [3H]维生素D3（3.6 - 3.8微居里；每只大鼠约等于25皮摩尔）。24小时后，我们检查它们的组织和血浆中是否存在放射性标记的1,25 - 二羟维生素D3。完整大鼠、假手术大鼠或输尿管结扎大鼠的血浆、骨骼和肠道中存在大量放射性物质，其色谱行为与 authentic 1,25 - 二羟维生素D3相同。然而，在急性肾切除大鼠的血浆、骨骼或肠道中未发现以类似于1,25 - 二羟维生素D3的方式洗脱的放射性。我们得出结论，在急性肾切除的活体大鼠中，血浆、骨骼或肠道中不存在我们所使用的灵敏技术可检测到量的1,25 - 二羟维生素D3。在维生素D缺乏大鼠肾切除后的24小时内，未观察到25 - 羟维生素D3向1,25 - 二羟维生素D3的转化。这一事实使人对非肾细胞体外产生1,25 - 二羟维生素D3作为一种体内现象的重要性产生怀疑。
