Isolation, Characterization, and Biological Activity of Retinyl Phosphate from Hamster Intestinal Epithelium

Epithelial cells from hamster small intestine, in short term culture, incorporated [carbinol-14C]retinol into a compound that is identical to synthetic retinyl phosphate, as judged by chromatography on DEAE-cellulose, silicic acid, and thin layers of silica gel. The biological compound displays the same absorption spectrum as does synthetic retinyl phosphate with a maximum at 325 nm. Hydrolysis with mild alkali yields anhydroretinol, as it does for synthetic retinyl phosphate, with absorption maxima at 388, 368, and 346 nm. Enzymic hydrolysis by alkaline phosphatase releases 9% of the radioactivity as [14C]retinol. Under the same conditions, 9% of synthetic retinyl phosphate is hydrolyzed to retinol. The biological compound was tested for biological activity. At a concentration of 5.5 x 10-8 M it was as active as retinol and retinyl phosphate in reversing keratinization induced in hamster tracheal epithelium by vitamin A deficiency. It is concluded that hamster intestinal cells synthesize retinyl phosphate.