Production of a group-specific antibody to 1 alpha,25-dihydroxyvitamin D and its derivatives having the 1 alpha,3 beta-dihydroxylated A-ring structure.

To obtain a group-specific antibody to 1 alpha,25-dihydroxyvitamin D and its derivatives having the 1 alpha,3 beta-dihydroxylated A-ring structure, 1 alpha-hydroxy-25,26,27-trinorvitamin D3-24-oic acid was synthesized as a haptenic derivative by a new convenient synthetic route. Three kinds of polyclonal antibodies were elicited in rabbits against the hapten conjugated with bovine serum albumin, and their specificity was examined by cross-reactivities in a radioimmunoassay procedure. One of the antibodies was found to show a suitable binding property by addition of a small amount of the plasma from vitamin D-deficient rats. Dose-response curves with measurable ranges applicable to biological specimens were obtained for 1 alpha,25-dihydroxyvitamin D3, 1 alpha,25-dihydroxyvitamin D2, (24R)-1 alpha,24,25-trihydroxyvitamin D3, (23S,25R)-1 alpha,25-dihydroxyvitamin D3 26,23-lactone, and 22-oxacalcitriol by the radioimmunoassay system using this improved antibody. The antibody will be widely useful for developing profile analyses of 1 alpha,25-dihydroxyvitamin D and its derivatives (metabolites or synthetic analogs) having the 1 alpha,3 beta-dihydroxylated A-ring, as well as immunoassays measuring each of these secosterols individually.