Intracellular binding proteins for retinol and retinoic acid in early and term human placentas.

Specific binding of both [3H]retinol and [3H]retinoic acid was observed in the cytosol fraction from term placentas and specific binding of [3H]retinol but not [3H]retinoic acid was detected in the cytosol fraction from placentas of 8-12 week pregnancies. The elution volume of the bound radioactivity on Sephadex G-100 column chromatography was within the range expected for proteins of molecular weight 14 500, in agreement with the results of others for cellular retinol- and retinoic acid-binding proteins from other tissues. The role of these proteins in mediating the effects of vitamin A on growth and differentiation of the placenta and fetus has yet to be determined.