Comparison of fetal and adult retinol and retinoic acid binding proteins in bovine serum and pigment epithelium.

Cellular retinol binding protein (CRBP) and cellular retinoic acid binding protein (CRABP) were assayed in bovine eye pigment epithelium (PE) cytosol from both early fetal and young adult animals. Both fetal and adult PE contain CRBP but only fetal PE contains CRABP. Blood retinol binding protein (RBP) was also assayed in serum from fetal and adult animals. Both fetal and adult serum contain RBP. A novel albumin adsorption technique (Affi-Gel Blue) combined with refinements of the sucrose gradient centrifugation technique provide a better assay method for retinoid receptors than polyacrylamide disc gel electrophoresis. Our findings support the hypothesis that retinoid receptors may cause or be the consequence of differentiation in animal tissues.