Vitamin D-Induced Calcium Binding Factor in Rat Intestinal Mucosa.

Abstract

Oral administration of 500 IU of vitamin D2 or vitamin D3 to rachitic rats resulted in the elaboration of a Ca binding factor detected in the supernatant fraction of duodenal mucosal homogenates at 72 hr. after vitamin administration. This factor was associated with the initial or protein containing portion of the supernatants after percolation through Sephadex G-25; indicating that the factor was a macromolecule, presumably a protein. Further separation of the supernatants by Sephadex G-100 gel filtration showed increased binding activity after vitamin D administration was mainly associated with only one of the protein peaks present in the Sephadex G-100 fractions. This particular peak was much less prominent in the fractionated supernatant of the mucosal homogenates from rachitic rats. Vitamin-D dependent binding activity is due to the presence of a specific Ca binding protein in the supernatant fraction of duodenal mucosal homogenates from vitamin D-treated rachitic rats.