Modification of the daily photoreceptor membrane shedding response in vitro by antioxidants

The shedding of rod outer segment disc membrane was investigated in a commonly used frog eyecup preparation, with respect to length of time in vitro. It was found that the amplitude, but not the timing, of the "dawn" (ie, when the lights are turned on) shedding response was increased threefold if the time in vitro was increased from 1.5-2 hr to 12-13 hr before dawn. After the overnight incubation, morphologic deterioration of the photoreceptors was not apparent by light or electron microscopy. The addition of the antioxidants, vitamin C or alpha-tocopherol (vitamin E), inhibited the increase in shedding, suggesting that it was induced by oxidation. These results help define conditions necessary for the maintenance of normal retinal metabolism in vitro. They also suggest a link between the amplitude of the dawn disc membrane shedding response and oxidation.