Photoreceptor outer segments: accelerated membrane renewal in rods after exposure to light

The rate of rod outer segment renewal in Rana pipiens tadpoles under constant light and under diurnal conditions of 12 or 2 hours light per day is significantly increased compared to that in animals in darkness. Furthermore, during 24 hours in light after 6 days in darkness the rate of renewal is three to four times that in darkness. In Xenopus laevis tadpoles the rate of renewal is more than five times greater during the first 8 hours of a normal diurnal cycle than during the following 16 hours. These observations demonstrate that bursts of renewal activity occur as a response to light, and suggest that a normal pattern of light alternating with darness plays a fundamental role in the regulation of rod outer segment turnover.