Effects of co-supplementation of iron with ascorbic acid on antioxidant--pro-oxidant balance in the guinea pig.

The relationship between intake of iron with ascorbic acid and their uptake into the plasma and liver of guinea pigs was studied. The influence on the antioxidant/pro-oxidant balance of liver microsomes was also determined. Animals were fed a standard pelleted diet low in iron and ascorbic acid for 35 days. The pellet diet was supplemented by oral dosing with a solution containing either maintenance dietary levels of ascorbic acid and iron, or one of three regimens that increased the dosage of these substances ten fold. There were no significant differences in animal growth rate or food intake between these regimens. Liver and plasma total ascorbate levels were significantly increased (p < 0.05) in animals receiving either ascorbic acid alone (liver 126 +/- 36 micrograms/g tissue wet wt. and plasma 51.7 +/- 17.0 microM; n = 9) or ascorbic acid and iron (105 +/- 18 micrograms/g and 40.3 +/- 15.3.0 microM; n = 8) compared to controls (84 +/- 36 micrograms/g and 15.3 +/- 8.5 microM; n = 11). Total iron levels in the liver (76.7 +/- 7.3 micrograms/g; control; n = 6) and plasma (2.4 +/- 0.03 mg/l; control) were not significantly raised in animals under these conditions of iron or ascorbate intake. Liver microsomes isolated from animals receiving iron had a greater susceptibility to oxidative stress in terms of malondialdehyde production during auto-oxidation compared to those from control animals under the same conditions. This effect was eliminated on combining ascorbic acid with the iron supplementation, suggesting that oral administration of vitamin C has a protective rather than a pro-oxidant effect under these circumstances.