Production rate and removal of rod outer segment material in vitamin A deficiency.

Normal albino rats were placed on a standardized vitamin A-deficient diet. The rate of rod outer segment renewal and removal was determined at varying levels of vitamin A deficiency by autoradiography. Increasing vitamin A deficiency causes a decreasing rate of photoreceptor outer segment renewal. The removal of rod outer segment material by the pigment epithelium normally takes ten days. The level of vitamin A deficiency did not change this time. Since rod outer segment production was slowed with deficiency, the amount of material being removed progressively became less as vitamin A deficiency increased. This finding suggests that effective phagocytic removal cannot take place until a time-related change occurs in the outer segment material.