title: Measurement of circulating 1,25-dihydroxyvitamin D in man. Changes in serum concentrations during treatment with 1 alpha-hydroxycholecalciferol.
abstract: A sensitive assay is described for measurement of circulating 1,25-dihydroxyvitamin D (1,25-(OH)2D) using rachitic chick intestinal cytosol binding protein. The metabolite was extracted from serum by diethyl ether and chromotographed on a Sephadex LH-20 column followed by high-pressure liquid chromatography. The concentration of 1,25-(OH)2D was then measured by a competitive protein-binding assay. The binding capacity of the protein was unchanged for 4 months. The inter- and intra-assay variations were both 11%. The standard curve was useful at serum concentrations ranging from 14 to 395 pmol/l (6 to 165 pg/ml). The normal mean concentration was 79.6 +/- 36.8 pmol/l (33.1 +/- 15.3 pg/ml). The serum 1,25-(OH)2D was studied in elderly subjects following administration of 1 alpha-hydroxycholecalciferol (1 alpha-OHD3) at different doses. Large variations occurred indicating individual rates of metabolism of 1,25-(OH)2D.
mesh_terms: D000284:Administration, Oral; D000293:Adolescent; D000328:Adult; D000368:Aged; D000818:Animals; D001667:Binding, Competitive; D001681:Biological Assay; D002645:Chickens; D002850:Chromatography, Gel; D002851:Chromatography, High Pressure Liquid; D003600:Cytosol / Q000378:metabolism; D004100:Dihydroxycholecalciferols / Q000097:blood*; D006801:Humans; D006887:Hydroxycholecalciferols / Q000008:administration & dosage / Q000097:blood* / Q000494:pharmacology*; D008297:Male; D008722:Methods; D008875:Middle Aged; D011485:Protein Binding
chemical_list: D004100:Dihydroxycholecalciferols; D006887:Hydroxycholecalciferols