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Nuclear Uptake of Retinoids: Autoradiographic Evidence in Retinoblastoma Cells In Vitro

The special role of vitamin A (retinol) in vision is well known (Wald, 1968). The more general role that vitamin A plays in differentiation and maintenance of epithelial tissues is less well understood. There are several interesting analogies, however, between vitamin A and the steroid hormones which may enable us to better understand the vitamin’s general mechanism of action (Wolf and De Luca, 1970). Both vitamin A and the hormones affect tissue development and growth and have specific intracellular receptors in target tissues (Bashor et al., 1973), including the neural retina (Wiggert et al., 1977~). We have recently presented preliminary biochemical evidence that retinoic acid, a normal metabolite of retinol, is preferentially taken up by nuclei ofretinoblastoma cells in culture (Wiggert et al., 1977b), again in a manner similar to the well-known accumulation of steroid hormones in target cell nuclei. In the present communication, we would like to present further evidence using alternative techniques that retinoic acid, but not retinol, is preferentially taken up in retinoblastoma nuclei and that it may be the “active” retinoid in these cultured human cells.