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. 1976 Sep;43(3):712-5.
doi: 10.1210/jcem-43-3-712.

Competition by 24,25-dihydroxycholecalciferol in the competitive protein binding radioassay of 25-hydroxycalciferol

J G Haddad Jr, C Min, J Walgate, T Hahn

Competition by 24,25-dihydroxycholecalciferol in the competitive protein binding radioassay of 25-hydroxycalciferol

J G Haddad Jr et al. J Clin Endocrinol Metab. 1976 Sep.

Abstract

24,25-dihydroxycholecalciferol (24,25-(OH)2D3) is equipotent to 25-hydroxycholecalciferol in the displacement of 3H25-OHD3 from rat serum binding sites, and is extracted by the ethanol procedure recommended in non-chromatographic competitive protein binding radioassays for 25-OHD. Serum 24,25-(OH)2D content was measured following 24,25-(OH)2D3 isolation from lipid extracts by liquid-gel partition chromatography. Since normal serum 24,25-(OH)2D concentration is appreciable, non-chromatographic 25-OHD assays most probably overestimate serum 25-OHD levels as a result of their recognition of 24,25-(OH)2D3.

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