title: Development and application of an alpha-face-specific radioimmunoassay for vitamin B12.
abstract: The first development of an alpha-face-specific radioimmunoassay for vitamin B12 is described. Sheep, fed a cobalt-deficient diet, and immunized with a conjugate between Co-beta carboxypropyl cobalamin and keyhole limpet hemocyanin, were used to produce antisera. The antisera crossreacted with Co-beta derivatives of vitamin B12, but did not crossreact with the alpha-face vitamin B12 analog cobinamide. The antisera were used to develop a sensitive and reproducible radioimmunoassay that was free from contamination with the nonspecific vitamin B12 binding protein, R-protein. Both the radioimmunoassay and measurements of plasma concentrations of methylmalonic acid were applied to the diagnosis of cobalt/vitamin B12 deficiency in sheep. The assay correlated well with a commercially available radioassay and did not falsely detect normal vitamin B12 concentration in plasma samples containing elevated concentrations of methylmalonic acid.
mesh_terms: D000818:Animals; D003035:Cobalt / Q000172:deficiency*; D006433:Hemocyanins; D007106:Immune Sera / Q000276:immunology; D007114:Immunization; D051379:Mice; D011817:Rabbits; D011863:Radioimmunoassay / Q000379:methods*; D012756:Sheep; D012757:Sheep Diseases / Q000175:diagnosis*; D014805:Vitamin B 12 / Q000097:blood* / Q000276:immunology; D014806:Vitamin B 12 Deficiency / Q000175:diagnosis / Q000662:veterinary*
chemical_list: D007106:Immune Sera; D003035:Cobalt; D006433:Hemocyanins; D014805:Vitamin B 12