Two biologically active metabolites of vitamin D3 have been isolated and identified as 25-hydroxy-vitamin D3(25-0H-D3) and 1,25-dihydroxyvitamin D3(1,25-diOH-D3). 25-OH-D3, originally denoted peak 4A, has been obtained from the blood of 1850 rachitic chicks who received a prior dose of tritiated vitamin D3. 1,25-diOH-D3, formerly referred to as peak 4B, was isolated from an in vitro reaction mixture containing 25-OH-D3, a NADPH generating system and kidney homogenate from rachitic chicks. Metabolites were purified by column chromatography on silicic acid, Sephadex LH-20 and Celite, and by countercurrent distribution. 15.4 μg of 25-OH-D3 and 22.8 μg of 1,25-diOH-D3 were isolated by these techniques and characterization was carried out by ultraviolet absorption spectrophotometry and mass spectrometry. These studies confirm earlier conclusions (based upon chromatographie data) that chick metabolite 4A is identical to the 25-OH-D3 metabolite isolated from pig blood by Blunt, DeLuca and Schnoes (Biochemistry 7, 3317(1968)). The data also substantiate the previous elucidation of the structure of chick peak 4B as 1,25-diOH-D3 and support its role as the hormonal form of vitamin D.
ASJC Scopus subject areas
- Molecular Biology