Retinoic acid-binding protein in normal tissues and experimental tumors

The tissue distribution of retinoic acid-binding protein (RABP) has been determined for tissues of chick embryos and young and adult rats and mice and has been compared with other published data. Although no species variability has been detected with tissue distribution of RABP, relatively more of the protein is detected in the tissues of young animals than in those of adult ones. This protein is below the limits of detection in the adult rat or mouse brains, whereas it was present in abundance in the embryonic and young brains. RABP is present in the epithelial cells but not in the connective tissue of skin. Besides brain, skin, testis, and eye, RABP is also detected in small quantities in the bladder prostate, uterus, trachea, and mammary glands of rats and mice. Although RABP could not be detected in normal lungs, this protein is found to be present in Lewis lung tumors and in lungs with metastatic Lewis lung foci. Of four chemically induced transplantable colon tumors of mice, two highly metastatic ones contained RABP, whereas the two nonmetastatic lines as well as normal colon did not.