On the Subcellular Location of Vitamin D Metabolites in Intestine

Following the intravenous injection of radioactive vitamin D, no radioactivity appeared in intestinal isolated according to the procedure of Marushige and Bonner, J. Mol. Biol., 15, 160 (1966). Instead the radioactivity of intestinal nuclei remained with a membrane fraction which is separated from at the initial step in the preparation. When chromatin was prepared by the method of Haussler, Myrtle, and Norman, J. Biol. Chem., 243, 4055 (1968) as much as 40% of the intestinal radioactivity appeared in the fraction in the case of chicks and 20% in the case of rats. However, the prepared by this method was heavily contamined with membranes and cell organelles whereas the Marushige and Bonner preparations were composed of homogeneous as revealed by electron microscopy. Chemical analysis and ultraviolet spectra confirmed the electron microscopic data. Thus the previous contention that intestinal is a major site of vitamin D metabolite location is without experimental basis.