THE BIOLOGICAL FUNCTION OF VITAMIN A ACID

Abstract

The general tissue functions of vitamin A that support growth and maintenance in the rat are served also by vitamin A acid; but since this substance is not reduced, it forms neither the alcohol, the form in which vitamin A is stored, nor the aldehyde (retinine) needed for the synthesis of visual pigments. For this reason, rats maintained on vitamin A acid, though growing normally and otherwise in good condition, become extremely night-blind, and eventually blind. The failure to form visual pigments also has specific anatomical consequences the outer segments of the visual cells deteriorate, followed by the loss of almost all the cells themselves, in an otherwise normal retina. These anatomical changes resemble those observed in certain hereditary forms of blindness and in human retinitis pigmentosa.