Receptors of 1,25-Dihydroxycholecalciferol in Rat Intestine

Following a 62.5-pmole dose of 1,25-dihydroxy-[3H]cholecalciferol, 80% of the 3H in intestinal mucosa of vitamin D-deficient rats is located in the crude nuclear debris fraction. Of the radioactivity associated with the crude nuclear debris fraction, 30 to 45% is found associated with pure chromatin while more than 50% of the radioactivity is either extranuclear or loosely bound to the nuclei. A low density protein fraction which apparently contains this radioactivity was isolated from the nuclear debris fraction. Both chromatin and this lipoprotein complex have highly specific binding activity for 1,25-dihydroxycholecalciferol.