Vitamin D3 Binding Protein in Rat Intestinal Mucosa

Vitamin D3 binding protein has been identified in the cytoplasm and nuclear fractions of rat intestinal mucosa. Each protein binds in vitro directly with vitamin D3-1, 2-3H. Cytoplasmic binding protein has little content of DNA, and nuclear binding protein contained DNA and a small amount of RNA. Its sedimentation constant was calculated as about 13S and 10S respectively by sucrose density gradient ultracentrifugation. Their different behaviours were also observed by the polyacrylamide gel disc electrophoresis. However, in the both cases the vitamin D3 binding was not affected with equal amount of cholesterol, 7-dehydrocholesterol, 17-β-estradiol and testosterone. Vitamin D3 transport from cytoplasm into nuclei was observed at a temperature of 37°, and not at the 2°. The vitamin D3 binding protein would be participated in the intracellular translocation of vitamin D3 of rat intestinal mucosa.