Abstract
The action of vitamin D_3 was discussed from the role of the specific binding proteins (SBP). SBP for vitamin D_3 metabolites in rat intestinal mucosa was analyzed by Sephadex G-200 and sucrose density gradient ultracentrifugation. Sedimentation constant of the binding protein for 25-hydroxycholecalciferol and 1,25-dihydroxycholecalciferol was 6,3S and 5,3S respectively. Calcium binding protein (CaBP) was analyzed by Sephadex G-100,DEAE-cellulose and sucrose density gradient ultracentrifugation. Three sorts of CaBP in rat intestinal mucosa were indentified as those of molecular weights ; >100,000,24,000〜27,000 and 13,000. Sterol carrier protein was also studied. The binding of 7-dehydrocholesterol to this protein was inhibited by vitamin D_3. From these results, the protein will participate in the intracellular movement of vitamin D_3 metabolites and physiological function of vitamin D_3.
