Radioimmunological determination of cellular retinol-binding protein in human tissue extracts

A sensitive and specific radioimmunoassay was developed for human cellular retinol-binding protein (CRBP) using antibodies raised in rabbits against purified human liver CRBP. The assay could determine concentrations of CRBP in extracts down to 8 micrograms/liter. CRBP could be demonstrated in all tissues investigated except in serum, and the same immunoreactive CRBP seemed to be present in all tissues. The highest concentrations were found in the gonads. In the gastrointestinal tract, the small intestine had a higher concentration than did stomach or colon. Muscle and skin had low concentrations of CRBP.