title: Sequential-saturation-type assay for serum 25-hydroxyvitamin D.
abstract: We describe a method for measuring 25-hydroxyvitamin D in serum. The serum is denatured with ethanol, and the extract purified by chromatography on silicic acid to prevent potential interference from vitamin D and by other substances. 25-Hydoxyvitamin D is assayed by sequential saturation analysis in Tris-HCI buffer, pH 8.6, containing the surfactant Triton X-405 (2 ml/liter) to solubilize the steroid. Diluter, unpurifed normal human serum is used as the binder. The method is sensitive and precise. The dose-response curve is linear. The assay normally gives high count rates (12 000 to 20 000 cpm for the zero standard) and consequently 25-hydroxyvitamin D of low specific activity can be used if necessary. Serum 25-hydroxyvitamin D was determined in normal and osteomalacic subjects.
mesh_terms: D001798:Blood Proteins / Q000378:metabolism; D002021:Buffers; D002850:Chromatography, Gel; D004100:Dihydroxycholecalciferols / Q000097:blood; D005260:Female; D006801:Humans; D006887:Hydroxycholecalciferols / Q000097:blood*; D066298:In Vitro Techniques; D008297:Male; D008722:Methods; D011485:Protein Binding; D012016:Reference Values; D013997:Time Factors; D014316:Tritium
chemical_list: D001798:Blood Proteins; D002021:Buffers; D004100:Dihydroxycholecalciferols; D006887:Hydroxycholecalciferols; D014316:Tritium