Alpha-tocopherol in the retinal outer segment of bovine eyes.

α-Tocopherol was identified in lipid extracts of bovine retinal outer segment (ROS) preparations. Positive identification was obtained by the thin layer chromatographic characteristics of the tocopherol form and its oxidation product α-tocopherylquinone, and by the ultraviolet spectrum of the oxidized and KBH4-reduced form of the tocopherylquinone. In the ROS preparations used, α-tocopherol chromanol was the predominant species, the quinone form accounting for 25% or less of the total. The concentration of α-tocopherol in the ROS preparations was about 0.1 mole α-tocopherol per mole rhodopsin, or about 1 nmole/mg, protein. Mitochondria from bovine retina contained about 0.4 nmole α-tocopherol per mg protein.