The objective of proposed in vivo as well as in vitro nutritional and biochemical research is to continue to define the mechanisms(s) of action of the important micronutrient vitamin A at the molecular level in organs other than the eye. The participation in the mode of vitamin action of two distinct specific intracellular cytoplasmic binding proteins for retionl (vitamin A alcohol) and for retinoic acid (vitamin A acid) purified to homogeneity from rat liver and testis will receive particular attention. In vitro studies are proposed how retinol and retinoic acid bound to their respective binding proteins interact with the cell nucleus changing thereby the genomic expression underlying cell differentiation. The in vivo studies are directed towards the elucidation of factor which regulate the levels of these binding proteins in various organs in adult and in neonatal rats. To this end sensitive radioimmunoassys developed for both binding proteins will be utilized.
