Immunohistochemical mapping of vitamin D-dependent calcium-binding protein in brain

The steroid hormone, 1,25-dihydroxycholecalciferol (1,25-(OH) sub(2)D sub(3)) causes the de novo) synthesis of a calcium-binding protein (D-CaBP). This protein is present in highest concentrations in intestine, kidney and shell gland, across which calcium is transported in relatively large amounts, but it is also found in smaller amounts in several other tissues, including brain. The area of brain with the highest D-CaBP concentration is the cerebellum, where the protein is found only in the Purkinje cells. The authors have now mapped D-CaBP immunohistochemically throughout the brain of chicks and rats and present here a list of all positive nuclei. Because certain of these neurones also contain 1,25-(OH) sub(2)D sub(3), the authors suggest that they are target cells for this hormone, thus broadening the functional significance of vitamin D to include the brain and implicating vitamin D in a more widespread action than simply a role in the calcium translocation mechanism of epithelial cells.