2 D 3 acts on mineral regulating target tissues such as intestine, kidney, parathyroid glands, and bone to participate in maintaining calcium and mineral homeostasis. Its predominant role is to enhance the intestinal absorption of dietary calcium and phosphorous. In the absence of adequate dietary calcium, reserves in the skeleton are mobilized to maintain appropriate serum calcium levels. Thus, one key physiological role of vitamin D is to preserve skeletal calcium by ensuring an adequate absorption of dietary calcium. In addition to the calciotropic role of this steroid hormone, vitamin D also functions in a number of other complex systems, such as promoting cellular differentiation.
Vitamin D is also a known regulator of osteoblast differentiation and function.
Thus, it is through an integrated series of diverse effects that vitamin D is thought to preserve and maintain the integrity of mineralized tissues. 2 D 3 with high affinity and high selectivity. This manuscript discusses structural, functional, and mechanistic aspects of VDR-mediated transactivation in osteoblasts. The emphasis is on the macromolecular interactions that are required for the regulatory activity of the VDR on osteoblast gene expression. This final aspect has been a fertile area of recent research in the nuclear receptor field and its implications in the mechanism of transcriptional regulation by the VDR in osteoblasts are now being realized.