α-Tocopherol in the developing rat retina: A high pressure liquid chromatographic analysis

High pressure liquid chromatography was used to measure a-tocopherol in the retinas of rats reared in a cyclic light or dark environment. These measurements were performed on extracts of whole retinas during the developmental period, 18–60 days, and on isolated ROS from adult animals. Similar α-tocopherol determinations were performed on retinas and isolated ROS following exposure of rats to intense visible light for 24 hr periods.The results show that a-tocopherol is chromatographically separated from the vitamin A derivatives found in the retina and is pure, as judged by mass spectrometry. In the retinas of cyclic light and dark reared rats, a-tocopherol accumulates in an age dependent fashion, so that at 60 days the level is nearly double that of animals at 18–20 days of age (P<0.001). Because the age dependent accumulation of rhodopsin is greater in dark reared rats, the average molar ratio of rhodopsin to α- tocopherol in the retina of dark reared animals is 25% higher than in cyclic light rats. Following exposure of rats to intense visible light for 24 hr periods, a-tocopherol concentrations in the retina were unchanged from the levels in control animals.In adult animals the concentration of a-tocopherol in ROS is 2.5–3.5 times higher than in whole retina. ROS from adult cyclic light reared rats also contain an average of 43% more a-tocopherol per mg protein than ROS from dark maintained animals (P < 0.005). The concentrations of α-tocopherol in ROS from intense light treated rats were 8–10% lower, but not significantly lower than the concentrations in ROS from control animals. However, a-tocopherol in the ROS of intense light exposed rats previously maintained in cyclic light, remained 40% higher than in ROS from dark reared animals. The differences in the rhodopsin to a-tocopherol ratio in retina and a-tocopherol concentrations in ROS from rats of the two light environments suggest that cyclic light reared animals may be better prepared to handle oxidative insult than dark reared rats.