Cellular retinol-binding protein. Quantitation and distribution.

The distribution of cellular retinol-binding protein was localized in three tissues involved in the transport of vitamin A using the peroxidase-antiperoxidase technique. In addition, a sensitive radioimmunoassay was developed to quantitate cellular retinol-binding protein in various tissues. In liver, the protein was found in the hepatocytes and in the perisinusoidal fat-storing cells. The columnar epithelial cells of the jejunum and the cells of the proximal tubuli also exhibit high concentrations of cellular retinol-binding protein. Estimations of the content of the protein in various tissues from normal and retinol-deficient rats showed that the retinol status did not affect the tissue levels or the subcellular distribution. The appearance of high amounts of this protein in cells involved in the dietary uptake, storage, mobilization, and resorption of vitamin A suggest that one function of the cellular retinol-binding protein is to act as a vehicle in the intracellular transport of retinol through these organs.