title: A bioassay capable of measuring 1 picogram of 1,25-dihydroxyvitamin D3.
abstract: Fetal rat bones in organ culture constitute a sensitive system for assay of the vitamin D metabolite, 1 alpha,25-dihydroxyvitamin D3. Significant bone resorption is obtained with as little as 2 pg 1,25-dihydroxyvitamin D3 after 48 h of culture and with 1 pg after 64 h of culture. In the current study, organ cultures of fetal rat bone are used as a bioassay for 1,25-dihydroxyvitamin D i normal human plasma, which was prepared for assay by extraction with dichloromethane, chromatography on Sephadex LH-20, and purification on silicic acid by high pressure liquid chromatography. The concentration of 1 alpha,25-dihydroxyvitamin D3 in normal adult human plasma was 24.8 +/- 2.0 pg/ml (n = 19) by this assay.
mesh_terms: D000818:Animals; D001681:Biological Assay; D001842:Bone and Bones / Q000187:drug effects; D002117:Calcitriol / Q000032:analysis* / Q000097:blood; D002118:Calcium / Q000378:metabolism; D005260:Female; D005333:Fetus; D007700:Kinetics; D008832:Microchemistry; D009924:Organ Culture Techniques; D010012:Osteogenesis / Q000187:drug effects; D011247:Pregnancy; D051381:Rats
chemical_list: D002117:Calcitriol; D002118:Calcium