Iron Absorption in the Rat: The Search for Possible Intestinal Mucosal Carriers

Halliday, June W.; Powell, Lawrie W.; Mack, Ulrich

doi:10.1111/j.1365-2141.1976.tb00194.x

Cited by 56 publications

(30 citation statements)

References 26 publications

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“…Several workers have described the presence of a protein in the intestinal mucosal cells of small laboratory animals that is similar, if not identical to circulating transferrin (29)(30)(31). Quantitative immunologic assays performed on homogenates of rat mucosal cells demonstrated that the concentration of mucosal transferrin varies directly with radioiron uptake by the mucosa (14).…”

Section: Discussionmentioning

confidence: 99%

Duodenal iron proteins in idiopathic hemochromatosis.

Whittaker¹,

Skikne²,

Covell³

et al. 1989

J. Clin. Invest.

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This study was undertaken to assess the relationship between iron absorption and the concentration of duodenal iron proteins in normal subjects and patients with idiopathic hemochromatosis (IH). Biopsies were obtained endoscopically from the duodenum in 17 normal subjects, 3 of whom were mildly iron deficient, and 7 patients with untreated IH. The absorption of both heme and nonheme iron was increased in IH despite a 20-fold elevation in serum ferritin. Immunoassays using MAb were used to measure transferrin, H-rich ferritin, and L-rich ferritin in mucosal samples. Mucosal transferrin concentrations in normal subjects did not correlate with either iron status or iron absorption, indicating that mucosal transferrin plays no physiological role in iron absorption. Mucosal transferrin was significantly lower in IH, presumably because of a decrease in mucosal transferrin receptors. Mucosal H and L ferritin concentrations were directly related to body iron stores and inversely related to iron absorption in normal subjects. In IFH, mucosal H and L ferritin failed to increase in parallel with the serum ferritin, but were appropriate for the level of iron absorption. The relationship of mucosal H/L ferritin in IH did not differ from that observed in normal subjects. Our findings indicate that the major abnormality in duodenal iron proteins in IH is a parallel decrease in the concentration of H-and L-rich ferritin. It is-not evident whether this is the result or the cause of the absorptive abnormality.

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Section: Discussionmentioning

confidence: 99%

Duodenal iron proteins in idiopathic hemochromatosis.

Whittaker¹,

Skikne²,

Covell³

et al. 1989

J. Clin. Invest.

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“…Both transferrin and ferritin have been found in the intestinal mucosa (8)(9)(10) and other mucosal iron binding proteins, similar in size and properties to trans-ferrin, have also been reported (11,12). In one species a claim has been made that the transferrin-like protein is unrelated immunologically (12).…”

Section: Introductionmentioning

confidence: 99%

Iron binding proteins of iron-absorbing rat intestinal mucosa.

Johnson¹,

Jacobs²,

Purves³

1983

J. Clin. Invest.

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A B S T R A C T The distribution and quantitation of the iron-binding proteins of rat small intestinal mucosa was studied, in iron-deficient and replete animals, to explore their role in the absorption of iron. Adsorption (mucosal uptake) of iron in in situ ligated loops of small intestinal mucosa was found to be uniform throughout the length of the small intestine whereas absorption (carcass uptake) showed a steep decreasing gradient from the duodenum to the ileum. The disrupted, in vivo labeled mucosal cells were fractionated by isopycnic centrifugation and transferrin and ferritin were quantitated by radioimmunoassay. Transferrin derived from mucosal cells was shown to have a higher affinity for the antibody than transferrin in serum. Of the transferrin present in the mucosal extract, only a portion could be accounted for by contamination from the serum; the proteolysis resistant and intrinsic transferrin may be mucosal cell specific. Transferrin was found in similar amounts in all regions of the small intestine, was not affected by iron loading but doubled in response to iron deficiency. Mucosal ferritin was found in greater amounts in the iron-absorbing areas of the intestine, increased in the duodenum of iron-loaded animals, and decreased in irondeficient animals. The incorporation of newly absorbed radioiron into ferritin was only found in iron absorbing regions and was completely inhibited by colchicine and cytochalasin-B, suggesting that ferritin was loaded with iron at the point of iron absorption and that the process is associated with vesicle movement and not simple diffusion. Transferrin and ferritin-specific immunoabsorption and also gel filtration established that no other soluble iron binding proteins were involved in absorption.Address reprint requests to Professor Jacobs.

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“…Iron deficiency in rats leads to an increase in transferrin levels in both the serum and the small intestine (13,14).…”

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confidence: 99%

“…The increase in intestinal transferrin is correlated with an increase in iron absorption, and this has lead to the hypothesis that transferrin may play a role in mediating iron absorption (13,14,17,18). Several lines of evidence support this idea.…”

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“…In addition, we were unable to detect any transferrin mRNA in the small intestine of normal rats (Table 1). Within the intestine, transferrin protein is primarily localized in and around the mucosal cells of the duodenum, where it increases in iron deficiency (13)(14)(15)(16). To maximize the likelihood of detecting any intestinal transferrin mRNA, we assayed samples of total nucleic acid isolated from duodenal mucosal cells from iron-deficient rats.…”

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confidence: 99%

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