Supplementation with alpha-tocopherol or a combination of alpha-tocopherol and ascorbic acid protects the gastrointestinal tract of iron-deficient rats against iron-induced oxidative damage during iron repletion.

Recently we have shown the susceptibility of Fe-deficient rat intestine to oxidative damage during Fe repletion. The role of dietary antioxidants like ascorbic acid, alpha-tocopherol and a combination of both in counteracting the oxidative stress was tested in this study. Five groups of thirteen weanling WKY female rats were fed with an Fe-deficient diet for a period of 5 weeks. Another set of thirteen rats received an Fe-sufficient diet and served as the control group (Con). Oral administration of either vehicle (D), 8 mg Fe alone (D+) or in the presence of 24 mg ascorbic acid (D+ + C), 40 mg alpha-tocopherol (D+ + E) or a combination of both (D+ + C + E) per d for 15 d was carried out in Fe-depleted rats. The impact of this treatment protocol on Fe status, oxidative stress and antioxidant status at the site of Fe absorption was assessed. It was observed that though the indicators of Fe status were normalised on Fe supplementation, the oxidative stress as reflected by the levels of both thiobarbituric-acid reactive substances (TBARS) and protein carbonyls were significantly greater in D+ and D+ + C compared to D+ + E, D+ + C + E and Con groups. The mucosal cell DNA damage was seen in D+, D+ + C and D+ + E groups on electrophoresis. Functional integrity as assessed by the activities of alkaline phosphatase and lys-ala-dipeptidyl aminopeptidase were normalized in all the groups treated with the antioxidant(s). There were significant positive alterations in some of the endogenous antiperoxidative systems and in serum caeruloplasmin activity in D+ + E and D+ + C + E groups. Paradoxically, serum ascorbate levels were significantly lower in D+ + C than in D+ + E and D+ + C + E groups. This could be due to the protection offered by alpha-tocopherol in the presence of Fe. It is concluded that supplementation of alpha-tocopherol alone or in combination with ascorbic acid protects the gastrointestinal tract of Fe-deficient rats against Fe-mediated oxidative damage during Fe repletion. However, ascorbic acid alone does not protect the gastrointestinal tract against Fe-induced oxidative stress.