Iron absorption in the iron-deficient rat.

Iron absorption in the iron-deficient rat was compared with that in the normal rat to better understand the regulation of this dynamic process. It was found that: Iron uptake by the iron-deficient intestinal mucosa was prolonged as a result of slower gastric release, particularly when larger doses of iron were employed. The increased mucosal uptake of ionized iron was not the result of increased adsorption, but instead appeared related to a metabolically active uptake process, whereas the increased mucosal uptake of transferrin iron was associated with increased numbers of mucosal cell membrane transferrin receptors.

Iron is not required in the lactoferrin stimulation of thymidine incorporation into the DNA of rat crypt enterocytes.

Lactoferrin has been identified as a factor in human colostrum that accounts for increased incorporation of thymidine into the DNA in an in vitro rat crypt enterocyte bioassay. We have examined lactoferrin-stimulated thymidine incorporation by comparing the effects of iron-free lactoferrin (apolactoferrin) with those of iron-saturated lactoferrin (diferric lactoferrin) under conditions that inhibit the transfer of iron between these iron-binding proteins in the bioassay system. In addition, we have compared the dose-response relationships of diferric lactoferrin and apolactoferrin.

Transferrin-reticulocyte cycle time in rat reticulocytes.

The uptake and release of 131I-labelled diferric transferrin by rat reticulocytes was examined both in vitro and in vivo. Cycle time in vitro was estimated to be 2.5 min in iron-deficient reticulocytes and 2.

Intact transferrin receptors in human plasma and their relation to erythropoiesis.

Intact transferrin receptor molecules complexed with transferrin were found in human plasma. The concentration of receptors was determined by an enzyme-linked immunosorbent assay that uses polyclonal antibodies. The mean concentration of 8,279 micrograms/L in 56 normal adults appears to be unrelated to age or sex.

A highly efficient chemical isolation procedure for the rat placental transferrin receptor.

A chemical method for the purification of rat placental transferrin receptor is described. After initial solubilization and concentration by ammonium sulfate precipitation, radioiron-tagged diferric transferrin was added to the dialyzed receptor fraction and subjected to anion-exchange chromatography on DEAE-Sephacel. Elution with a Tris-HCl buffer gradient yields a single fraction of radioactivity containing both free transferrin and the receptor-transferrin as a complex.