The metabolism and functions of XXXX .

@entity4772 @entity11089 @entity4880 @entity3873 @entity70884 @entity70882 @entity70883 @entity14645 @entity460 @entity70885 @entity35 @entity3151 @entity14951 @entity560
@entity560 functions by stimulating intestinal @entity460 and @entity3151 absorption, by stimulating bone @entity460 mobilization, and by increasing renal reabsorption of @entity460 in the distal tubule. These functions on bone and possibly kidney, but not intestine, require the parathyroid hormone. As a result of these functions, serum @entity460 and @entity3151 concentrations are elevated to supersaturating levels required for the mineralization of bone to prevent @entity11089 , @entity4772 , and @entity14645 tetany. Recent experiments demonstrate that maintaining serum @entity460 and @entity3151 levels in @entity560 -deficient @entity35 in the normal range results in normal bone growth and mineralization. However, increased calcification results because bone resorption by osteoclasts is a @entity560 -dependent process. Thus, bone resorption, modeling and remodeling must be considered @entity560 -dependent processes. @entity560 must be metabolized to @entity14951 by the liver and subsequently by the kidney to @entity3873 before function. @entity3873 is metabolized to a C-23 @entity4880 ( @entity70882 ) but the pathway is unknown. Although @entity14951 is metabolized to @entity70883 , @entity70884 and @entity70885 , these pathways play no role in the function of @entity560 as shown by appropriate fluoro analogs of @entity14951 . @entity3873 binds to a specific receptor in the intestinal nuclei to elicit a stimulation of @entity460 transport. @entity3873 plus the receptor causes transcription of specific genes that code for @entity460 and @entity3151 transport proteins. Only one protein, the @entity460 binding protein, has been identified as being @entity560 dependent. Two others have been described, but no clear description of the molecular mechanism of action of @entity3873 is yet available.
