© IUPAC RECENT DEVELOPMENTS IN STUDIES ON BIOLOGICAL FUNCTIONS OF VITAMIN A IN NORMAL AND TRANSFORMED TISSUES

Abstract — A biochemical pathway of phosphorylation and glycosylation of vitamin A has recently been found in hepatic, intestinal and epidermal tissues. More recent work suggests that mannosylretinylphosphate functions as a donor of mannose to membrane glycoconjugates. These reactions might ultimately explain the effects of vitamin A deficiency and some of the effects of excess vitamin A on biological systems. Studies of the effect of retinoids on cellular in vitro systems showed an increase in the adhesive properties of spontaneously-transformed mouse fibro-blasts in culture (Balb/c 3T12-3 cells). These cells are usually detached from the culture gish surface ip an EDTA adhesion assay. After culturing in presence of 3.3 x l0 to 3.3 x lOM retinol or retinoic acid the cells are no longer lifted from the plate and their morphology and adhesion resemble those of normal fibroblasts. This phenomenon of increased adhesion is observed as early as two days after exposure to the retinoid and it is readily reversible upon culturing in medium without exogenous retinoid. A variety of retinoids wa