RECIPROCAL PROTECTIVE EFFECTS OF ALL-TRANS RETINOL AND ALPHA-TOCOPHEROL DURING LIPID-PEROXIDATION IN RETINAL MEMBRANES

Interactions between vitamin A and vitamin E in suppressing lipid pero xidation were observed in bovine retinal membrane preparations submitt ed to peroxidative injury by the water soluble azo initiator 2,2'-azob is(2 -amidino-propane) hydrochloride (AAPH). Incorporation of 0.75 mno l mg prot(-1) all-trans retinol, an amount comparable with that of the endogenous alpha-tocopherol, significantly elongated the induction ti me preceding the release of TBA-reactive lipid peroxidation products, and reduced the consumption rate of the endogenous alpha-tocopherol. O n the other hand, all-trans retinol was not able to induce any delay t o the onset of lipid peroxidation when incorporated in membranes depri ved of endogenous alpha-tocopherol by exposure to UV light, although T BARS produced within 60 min decreased slightly. Consumption of all-tra ns retinol during peroxidation was more rapid when all-trans retinol w as incorporated in membranes deprived of alpha-tocopherol than in nati ve membranes. These data suggest that reciprocal protective effects be tween vitamin A and vitamin E may strongly contribute to the defence o f membranes against oxidative stress.