Vitamin A receptors in normal and dystrophic human retina

Abstract

VITAMIN A is necessary for normal development and functioning of most tissues of the body^1,2. It is uniquely important for the retina in that, in addition to its possible general role in cellular metabolism, it participates in the visual process as the prosthetic unit for rhodopsin. This takes place in specialised regions of the photoreceptor cell called rod outer segments (ROS). Little is known, however, about uptake, binding and translocation of retinol, the alcohol form of vitamin A, in the photoreceptor unit. A specific 2S receptor for retinol of molecular weight about 17,000 has been described in several animal tissues^3,4. Retinol receptors are also present in retina and pigment epithelium^5–9. In addition, we have recently found that an 8S receptor is present in retina and brain of most but not all animal species tested⁶. We report here that normal human retina exhibits both a 2S and 8S binding species for retinol but that only the 2S species is observed in the retina of a patient who had retinitis pigmentosa (RP).