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Enhanced Fe³⁺-Reducing Capacity Does Not Seem To Play a Major Role in Increasing Iron Absorption in Iron-Deficient Rats^1,2,

Elizabeth M. Wien^*,,3 and Darrell R. van Campen^*

^* U.S. Department of Agriculture-Agriculture Research Service, Plant, Soil and Nutrition Laboratory, Ithaca, NY 14853 Division of Nutritional Sciences, Cornell University, Ithaca, NY 14853

Some eucaryotic organisms, including many plants, yeast and mice, have a higher iron uptake during iron deficiency because the capacity to reduce Fe³⁺ from the environment to Fe²⁺ is greatly enhanced. To determine whether this occurs in rats, a common experimental model for iron absorption in humans, we compared the in vivo capacity to reduce intraluminal Fe³⁺ in iron-deficient and normal rats. We also measured potential Fe³⁺-reducing components within the intestinal lumen and on the mucosal surface. Iron-reducing capacity was higher in iron-deficient rats, by a significant (P = 0.026) but modest 20%, in parallel with higher mucosal weight (R² = 0.501, P = 0.003). In vitro iron reduction by lumen contents was correlated with mucosal weight, even though mucosal tissue was not present in the assays. This capacity was not related to ascorbic acid, glutathione or other nonprotein sulfhydryls. Mucosal ferric reductase activity was higher in iron-deficient rats in parallel with higher tissue weight, but the specific activity did not differ and the higher total activity was not associated with the brush border fraction. The role of endogenous Fe³⁺ reduction in regulating iron absorption should be investigated in humans and in other experimental models.

KEY WORDS: • rats • iron • iron deficiency • absorption • ferric

¹ Mention of a trademark or proprietary product does not constitute a guarantee or warranty of the product by the U.S. Department of Agriculture and does not imply its approval to the exclusion of other products that may be suitable.

² The costs of publication of this article were defrayed in part by the payment of page charges. This article must therefore be hereby marked "advertisement" in accordance with 18 USC section 1734 solely to indicate this fact.

³ To whom correspondence should be addressed.

Manuscript received 29 November 1993. Revision accepted 15 April 1994.