Selective inhibition of the non-enzymatic lipid peroxidation of phosphatidylserine in rod outer segments by alpha-tocopherol.
In the present study it was investigated if alpha-tocopherol shows protection against in vitro lipid peroxidation of phospholipids located in rod outer segment membranes (ROS). After incubation of ROS in an ascorbate-Fe2+ system, at 37 degrees C during 160 min, the total cpm originated from light emission (chemiluminescence) was found to be lower in those membranes incubated in the presence of alpha-tocopherol. The fatty acid composition of total lipids isolated from rod outer segment membranes was substantially modified when subjected to non-enzymatic lipid peroxidation with a considerable decrease of docosahexaenoic acid (22:6 n-3). The incorporation of alpha-tocopherol (0.35 micromol/mg protein) produce a 43.37% inhibition of the lipid peroxidation process evaluated as chemiluminescence (total cpm originated in 160 min). The phospholipid species containing the highest amount of docosahexaenoic acid: phosphatidylethanolamine and phosphatidylserine were more affected than phosphatidylcholine during the lipid peroxidation process. Not all phospholipids, however, were equally protected after the addition of alpha-tocopherol to the incubation medium. Phosphatidylcholine and phosphatidylethanolamine, were not protected by alpha-tocopherol, the vitamin provides selective antioxidant protection only for phosphatidylserine. These results indicate that alpha-tocopherol may act as antioxidant protecting rod outer segment membranes from deleterious effect by a selective mechanism that diminishes the loss of docosahexaenoic acid from phosphatidylserine.
Terrasa
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Cátedra de Bioquímica, Facultad de Ciencias Veterinarias, Universidad Nacional de La Plata, Argentina.
Guajardo
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Catalá
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D000818:Animals; D000975:Antioxidants / Q000494:pharmacology; D001205:Ascorbic Acid / Q000494:pharmacology; D002417:Cattle; D005227:Fatty Acids / Q000378:metabolism; D015227:Lipid Peroxidation / Q000187:drug effects* / Q000502:physiology*; D008163:Luminescent Measurements; D008563:Membrane Lipids / Q000737:chemistry / Q000378:metabolism; D010718:Phosphatidylserines / Q000378:metabolism*; D012374:Rod Cell Outer Segment / Q000187:drug effects / Q000378:metabolism*; D014810:Vitamin E / Q000494:pharmacology*
D000975:Antioxidants; D005227:Fatty Acids; D008563:Membrane Lipids; D010718:Phosphatidylserines; D014810:Vitamin E; D001205:Ascorbic Acid