The Association of a Metabolite of Vitamin D3 with Intestinal Mucosa Chromatin in Vivo

Abstract

Abstract Administration of a physiological dose of radioactive vitamin D3 to vitamin D-deficient chicks results in a localization of the radioactivity isolated from intestinal mucosa within the nuclear chromatin fraction. Extraction and chromatography of this chromatin-bound radioactivity in several systems indicates that 87% of it exists as a polar metabolite of vitamin D3. This polar metabolite has biological activity equivalent to the parent vitamin. The association of this metabolite with the chromatin fraction occurs only in the target intestinal mucosa and is specifically inhibited by pretreatment of the rachitic chick with nonradioactive vitamin D3 or vitamin D3 analogues such as vitamin D2 and dihydrotachysterol3. The time course of appearance of the polar metabolite in the entire intestine parallels the location of radioactivity in the chromatin fraction and is consistent with the lag in the physiological response to vitamin D.