Determination of vitamin D status by radioimmunoassay with an 125I-labeled tracer

Abstract

We report here the first radioimmunoassay for a vitamin D metabolite utilizing a radioiodinated tracer. Antibodies were generated in a goat immunized with the vitamin D analog 23, 24, 25, 26, 27-pentanor-C(22)-carboxylic acid of vitamin D, coupled directly with bovine serum albumin. The 125I-labeled tracer was prepared by reacting a 3-amino-propyl derivative of vitamin D-C(22)-amide with Bolton-Hunter reagent. The primary antiserum, used at a 15,000-fold final dilution, cross-reacted equally with all cholecalciferol and ergocalciferol metabolites tested except 1,25-dihydroxycalciferol metabolites and the parent calciferols; the antiserum did not cross-react with dihydrotachysterol. Calibrators were prepared in vitamin D-stripped human serum. 25-Hydroxycholecalciferol was quantitatively extracted from serum or plasma (50 microL) with acetonitrile. The assay consists of a 90-min incubation at room temperature with primary antiserum, followed by a 20-min incubation with a second antiserum and separation of bound from free fractions by centrifugation. The detection limit of the assay was 2.8 micrograms/L for 25-hydroxycholecalciferol. Results with the present assay compared well with those from a liquid-chromatographic procedure involving specific ultraviolet detection of 25-hydroxycalciferol in plasma.

Sporadic and MEN1-Related Primary Hyperparathyroidism: Differences in Clinical Expression and Severity

“…(17) Our finding of a similar prevalence of urolithiasis in MEN1-related PHPT patients compared with sPHPT patients, despite younger age, suggests higher stone disease activity in MEN1-related PHPT. It is also important to consider that, because some previous studies have used different criteria for diagnosing MEN1, (12,13) the results obtained may be not fully comparable with those of this one.…”

“…Serum intact PTH was measured by a chemiluminescent method (Nichols Institute Diagnostic, San Juan Capistrano, CA, USA), with intra-and interassay CVs of 5.1% and 8.2%, respectively (reference interval: 10-60 pg/ml or 10-60 ng/liter), and 25(OH)D 3 by radioimmunoassay (RIA; DiaSorin) as previously described. (12) Reference intervals for Ca ab adj , Ca 2+ , and PTH are derived from a normal population recruited in our laboratory.…”

Low 25(OH) vitamin D3 levels are associated with adverse outcome in newly diagnosed, intensively treated adult acute myeloid leukemia

“…18 Samples from the healthy volunteers were assayed in the laboratory of Dr. Bruce W. Hollis using the same radioimmunoassay. 17 Serum 25(OH) vitamin D 3 measurements and normal ranges in both laboratories were the same.…”

Effects of fractionated colostrum replacer and vitamins A, D, and E on haptoglobin and clinical health in neonatal Holstein calves challenged with Mycobacterium avium ssp. paratuberculosis

“…The samples were then centrifuged at 2,000 × g for 10 min at room temperature, and the pellet was discarded. The RIA then was conducted as described by Hollis et al (1993). Retinol and α-tocopherol were quantified in 6 milk samples representative of the entire study period by using procedures already described.…”