The active form of vitamin D, 1alpha,25-dihydroxyvitamin D3 (1,25(OH)2D3) is critical for regulation of serum calcium and phosphorus levels and for proper maintenance of bone mineralization and neuromuscular function. Biological effects of 1,25(OH)2D3 are mediated through a nuclear steroid hormone receptor, known as the vitamin D receptor (VDR). The discovery of VDR in a number of different cell and tissue types, suggests that the physiological role of vitamin D may extend beyond the regulation of calcium homeostasis and bone function. Unfortunately, identification of tissues expressing VDR has been controversial due to low abundance of the receptor and quality of the antibodies used. Therefore, we elected to characterize a panel of commercially available VDR antibodies in order to identify antibodies with high specificity and sensitivity. To address these objectives, we have used multiple immunoassays to determine VDR expression in tissues from several organs from multiple species employing tissues from VDR knockout mice as critical negative controls. Many of the antibodies tested showed nonspecific binding that can account for divergent reports. However, one antibody, identified as D-6, is highly specific and extremely sensitive. The specificity, sensitivity, and versatility of this antibody make it the preferred antibody for identifying VDR expression in target tissues using immunological methods.
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