The hormonal form of vitamin D, 1,25-dihydroxyvitamin D3 (1,25(OH)2D3), acts by binding initially to cytoplasmic receptors in target cells. Although 1,25(OH)2D3 receptors have been well characterized in peripheral mineral translocating tissues like intestine, bone, and kidney, little information beyond autoradiographic analysis is available on the possible binding of 1,25(OH)2D3 in central regulatory sites such as brain. Of particular interest is the pituitary gland since growth hormone and prolactin are thought to affect 1,25(OH)2D3 biosynthesis in kidney. We have utilized sucrose gradient sedimentation, saturation analysis, and DNA-cellulose chromatography to show here that normal rat pituitary cytosol contains a receptor-like component which binds 1,25(OH)2D3 with specificity and high affinity (K(d)=5x10-10 M). This macromolecule sediments at 3.3 S in high salt sucrose gradients, but is difficult to demonstrate in cytosol prepared from whole pituitaries because of excessive contamination by a 5.8 S serum-derived protein that binds the hormone as well as its 25-hydroxyvitamin D3 precursor. Enhancement of the 3.3 S 1,25(OH)2D3 binder relative to the 5.8 S protein can be achieved by incubating pituitary quarters with labeled hormone and washing prior to preparation of cytosol. However, the clearest demonstration of the 3.3 S receptor for 1,25(OH)2D3 results when freshly dispersed anterior pituitary cells serve as the source of cytosol. The receptor-like component also adsorbs to DNA-cellulose and elutes at a KCl concentration (0.25 M) identical with that of rat kidney cytosol receptor for 1,25(OH)2D3. Since this receptor-like molecule has biochemical properties very similar to that of other 1,25(OH)2D3 receptors, we suggest that the 1,25(OH)2D3 hormone may function in the pituitary gland.
|Original language||English (US)|
|Number of pages||4|
|Journal||Journal of Biological Chemistry|
|Publication status||Published - 1980|
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