Transferrin receptor affinity and iron transport in the human placenta

Brown, Peter J.; Molloy, C.M.; Johnson, Peter

doi:10.1016/s0143-4004(82)80014-3

Cited by 29 publications

(6 citation statements)

References 23 publications

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“…1) as the injected diferric transferrin loses much of its iron and is partly converted to apotransferin with the lower affinity for the placental receptors. By contrast to the present results Brown, Molloy & Johnson (1982) reported similar binding constants for the reaction of apo-and differic human transferrin to human placental syncytiotrophoblast microvillous plasma membrane preparations. Whether this is due to species or methodological differences is uncertain, but it should be noted that Brown and his associates did not take precautions against contamination of the apotransferrin by iron from the placental material.…”

Section: Discussioncontrasting

confidence: 99%

Distribution of Transferrin and Transferrin Receptors in the Rabbit Placenta

1983

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SUMMARYThe quantity and distribution of transferrin and transferrin-binding sites in the placenta were investigated in rabbits on the 28th-29th days of pregnancy. The animals were injected intravenously with a mixture of 59Fe-121I-labelled rabbit diferric transferrin and 131I-labelled rabbit albumin. The binding of transferrin to placentas removed 3-75 min later was determined by using the 13II-labelled albumin values to correct for tissue content of plasma. Mean values for transferrin binding of 1460 and 560 ,ug/g tissue were obtained 3-15 and 45-75 min after injection, respectively. Gel filtration ofplacental extracts prepared with the non-ionic detergent, Teric 12A9, showed that the 125I-labelled transferrin bound to a large molecular weight component which had the properties of a specific receptor. The receptor had a higher affinity for differic transferrin than for apotransferrin. The subcellular distribution of transferrin binding sites was determined by differential centrifugation of placental homogenates and by electron microscope autoradiography. The results with the former method indicated that the transferrin was bound to the microsomal fraction of the cells. Autoradiography showed that the majority of the transferrin molecules were at intracellular sites, mainly on the membrane of intracellular vesicles. It is concluded that iron-containing transferrin molecules enter the trophoblast cells by endocytosis or via a canalicular system after binding to cell membrane receptors. The higher affinity of the receptors for diferric transferrin than for apotransferrin explains the difference in amount of transferrin binding found within 15 min of injecting labelled diferric transferrin and that found 45-75 min later when much of the iron had been removed from the transferrin.

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Section: Discussioncontrasting

confidence: 99%

Distribution of Transferrin and Transferrin Receptors in the Rabbit Placenta

1983

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“…The model, as proposed by Morgan (40) and supported by morphological (4 1) and isotopic data (42), proposes that transfemn binds to a specific membrane receptor, that the transferrin-receptor complex is internalized by endocytosis, that the iron is released inside the cell, and that the apotransferrin exits from the cell. This model has since been demonstrated in many cell types and species (43)(44)(45)(46). A mechanism for iron donation similar to the model proposed for transfemn can be envisioned for lactoferrin in the brush border membrane and is supported in part by the finding of immunologically intact lactofemn in the feces of breast fed infants (I 2, 13).…”

Section: Discussionmentioning

confidence: 79%

Isolation and Characterization of Rhesus Monkey Milk Lactoferrin

Davidson

Lönnerdal

1986

Pediatr Res

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“…Iron is transported across the placental membrane by an active process, which is mediated via binding of maternal transferrin bound iron to transferrin receptors in placenta and subsequent transfer of iron into the fetal circulation (50)(51)(52). The efficiency of this transport system implies that iron deficiency in the newborn is encountered only at extreme iron deficiency in the mother.…”

Section: Iron Status In Newborn Babiesmentioning

confidence: 99%