Kinetics of the subcellular distribution of iron and cobalt in the intestinal mucosa of the rat.

A differential centrifugation technique was used to compare the subcellular distribution of labeled iron (Fe) and cobalt (Co) in iron-deficient animals (FeD), in which transport was active, with iron-loaded animals (FeL), in which transport was by diffusion. In FeL the amount of Fe and Co in each subcellular fraction was dependent upon dose; there was a linear relation between the amount of Fe or Co in each fraction and metal absorption. In FeD a curvilinear relation was noted between both Fe dose and absorption, and the amount of Fe in the particulate fractions I and II. In contrast, a linear relation was noted between both dose and absorption, and the smaller amounts of Fe in the other fractions. Most of the Co was in V ("soluble"), and the relation between Co in all the fractions and absorption was linear. The addition of Co to the Fe test dose was associated with a decrease in Fe in I and II. The results suggest that a constituent(s) in the particulate fractions I and II is involved in the enhanced absorption of Fe in FeD. The subcellular fraction responsible for the increased Co absorption in FeD was not identified.