BINDING OF VITAMIN-D TO LOW-DENSITY-LIPOPROTEIN (LDL) AND LDL RECEPTOR-MEDIATED PATHWAY INTO CELLS

The present study was undertaken to identify serum components other th an vitamin D-binding proteins that bind to 1,25(OH)(2) D-3, and its an alog. The binding rate of 1,25(OH)(2) D-3, 22-oxa-1,25(OH)(2)D-3 (OCT) or 25(OH) D-3 to total lipoprotein(TLP) represented 16.7%, 4.65%, and 3.11% of total counts added, respectively. Polyacrylamide gel electro phoresis of the TLP revealed that 1,25(OH)(2) D-3 and OCT were associa ted with LDL. The binding studies of OCT-bound LDL to the fibroblasts showed specific pathway to the cells mediated by LDL-receptor. These f indings may have important implications in understanding the mechanism s of the diverse biological actions of 1,25(OH)(2) D-3 and in designin g a novel delivery system for vitamin D analogs. (C) 1995 Academic Pre ss, Inc.