INCREASED SUSCEPTIBILITY OF CELLULAR MEMBRANES TO THE INDUCTION OF OXIDATIVE STRESS AFTER INGESTION OF HIGH-DOSES OF FISH OIL - EFFECT OF AGING AND PROTECTIVE ACTION OF DL-ALPHA TOCOPHEROL SUPPLEMENTATION

Feeding young and aged rats (2 and 18 months old, respectively) with sardine oil (10 g/kg body weight) for 14 days increases the content of eicosapentaenoic acid and docosahexaenoic acid in erythrocyte membranes. These changes are associated with an increased membrane susceptibility to the induction of oxidative stress. Supplementation of the dietary oil with dl-alpha tocopherol (1 g/kg oil) protects the membranes from young rats against this increased susceptibility, while membranes from aged animals appear equally susceptible to oxidation when compared with membranes obtained from rats fed nonsupplemented oil. Following fish oil ingestion, plasma and membrane dl-alpha tocopherol levels are reduced to undetectable levels. Supplementation of the oil with the antioxidant, restores dl-alpha tocopherol pool but to a different level in young and aged animals. The differential response of membranes from young and aged rats to the induction of oxidative stress can be ascribed to a different membrane availability of dl-alpha tocopherol and therefore to a different free radical scavenging capacity.