A new enzyme-linked immunosorbant assay for the measurement of human vitamin D receptor

The hormonal actions of 1 alpha ,25-dihydroxyvitamin D-3 [1,25(OH)(2)D-3] a re mediated by its cognate receptor protein, the vitamin D receptor (VDR). Despite the growing importance of the VDR system as a modulator of cell gro wth and differentiation, convenient assays for quantitative measurement of VDR are not readily available, and [H-3]1,25(OH)(2)D-3 ligand binding assay s remain the standard method. In this paper, we present data to validate an d characterize the usefulness of a new VDR enzyme-linked immunosorbant assa y (ELISA) kit developed for the measurement of VDR in biological samples, I n this assay, samples are added to microtitration wells coated with anti-VD R antibody and incubated with a second anti-VDR antibody that is biotinylat ed, The antibody receptor complex is then detected with streptavidin-labele d horseradish peroxidase followed by incubation with a chromogenic substrat e, tetramethylbenzidine. The assay was found to be sensitive and accurate f or measurements of VDR and compared favorably with the conventional radioli gand binding assay (RBA). The interassay variation ranged from 5% to 25% an d the intraassay variation was less than 5%. The ELISA presents several adv antages over existing methodology, including the use of nonradioactive dete ction systems, lower protein and sample volume requirements, as well as con venience and speed, The assay can be completed in as short a time as 3 h, a voiding overnight incubations, Data are also presented to demonstrate the a bility of the ELISA to detect both occupied and unoccupied VDR, making it a valuable research tool in settings where 1,25(OH)(2)D-3 is present. Howeve r, the ELISA, as currently formulated, is only useful for the detection of human VDR. (Rone 28:319-326; 2001) (C) 2001 by Elsevier Science Inc. All ri ghts reserved.