Exchange of iron and transferrin across endothelial surfaces in the rat and rabbit

Morgan, Evan H.

doi:10.1113/jphysiol.1963.sp007260

Cited by 18 publications

(7 citation statements)

References 22 publications

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“…Although our results are highly reproducible we have no adequate explanation for them. It should be noted that the concentration of transferrin in tissue fluids is of the order of lop6 M-10p5 M (Morgan, 1963), with about 30% of its iron binding sites occupied. In iron deficiency states, however, transferrin may be less than 5% iron saturated (Wintrobe, 1975).…”

Section: Discussionmentioning

confidence: 99%

Transferrin receptor expression during exponential and plateau phase growth of human tumour cells in culture

Musgrove

Rugg

Taylor

et al. 1984

Journal Cellular Physiology

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Transferrin receptor expression by the human tumour cell lines CCRF-CEM leukaemia and PMC-22B melanoma was studied, measuring the specific binding of fluorescein isothiocyanate (FITC)-labelled transferrin using a fluorescence-activated cell sorter. By measuring the fluorescence of cells stained at subsaturating concentrations of conjugate it was possible to calculate the average numbers of receptors per cell and the binding affinity by Scatchard analysis. These values (1.9 X 10(5) binding sites/cell, KA 1.2 X 10(9) M-1 for CCRF-CEM during exponential growth and 6.9 X 10(4) binding sites/cell, KA 1.4 X 10(-9) M-1 for PMC-22B) are in close agreement with previously published data obtained using radiolabelled transferrin. The present method, however, allowed the transferrin receptor expression of individual cells within a population to be measured and thus it has been possible to test the hypothesis that transferrin receptor is a marker for cycling cells. Frequency-distribution histograms of transferrin receptor showed a wide range of values for both cell lines during exponential growth. When the extreme ranges were sorted and the cells examined for cellular DNA content it was found that those with the highest transferrin receptor expression were enriched with cells in S, G2, and M phases of the cell cycle, whereas those with low transferrin receptor expression were mainly in G1. However, two-parameter-correlated dot plots of transferrin receptor expression versus DNA content showed there was considerable overlap between the ranges of receptor expression for the different cell cycle compartments. Using a stathmokinetic method we have measured the proportion of quiescent cells in fed plateau phase cultures. Transferrin receptor expression was downgraded under these growth conditions but, contrary to expectation, the decline affected the population uniformly, without the emergence of a distinct, transferrin receptor-negative subpopulation corresponding to the increasing proportion of quiescent cells. Thus, although transferrin receptor expression bears some relation to cell cycle phase and reflects the proliferative activity of populations of cells, it is incapable of identifying individual cells which are out of cycle.

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Section: Discussionmentioning

confidence: 99%

Transferrin receptor expression during exponential and plateau phase growth of human tumour cells in culture

Musgrove

Rugg

Taylor

et al. 1984

Journal Cellular Physiology

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“…This type of result has not been observed following the intravenous injection of radioiron bound to transferrin. In such cases the lymph concentration of radioiron remains lower than that of the plasma during short term experiments like those described herein [Ehrenstein, 1956;Wasserman, Sharney, Gevirtz, Schwartz, Weintraub, Tendler, Dumont, Dreiling and Witte, 1964;Morgan, 1963]. Hence, it appears likely that the relatively high concentration of radioiron in the lymph during the latter part of the present experiments was the result of iron passing preferentially from mucosa to lymph, not to plasma as occurred during the earlier phases of absorption.…”

Section: Discussionmentioning

confidence: 72%

“…1, '25I-labelled transferrin injected intravenously appeared in the lymph much more slowly than did 59Fe administered intragastrically. It has been shown that iron remains bound to transferrin during its passage from plasma to interstitial fluid and lymph [Morgan, 1963]. Hence, absorbed iron which entered the plasma and bound to transferrin would be expected to pass into the lymph much more slowly than was observed.…”

Section: Discussionmentioning

confidence: 97%

“…Purification anid labelling of proteins Transferrin and albumin were isolated from rat serum as described previously [Morgan, 1963;Gardiner and Morgan, 1974] and were labelled with 125J or "'lI by the iodine monochloride method [McFarlane, 1963]. Some preparations of transferrin were also labelled with radioiron by the addition of 59Fe as its complex with nitrilotriacetate to apotransferrin [Hemmaplardh and Morgan, 1974].…”

Section: Aniimalsmentioning

confidence: 99%

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The Role of Plasma Transferrin in Iron Absorption in the Rat

Morgan

1980

Exp Physiol

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The question of whether plasma transferrin acts as a carrier of iron from intestinal mucosal cells to the blood plasma was investigated in a series of experiments in the rat. By thoracic duct cannulation and collection of lymph during absorption it was confirmed that nearly all absorbed iron passes direcly to portal blood. The total rate of transcapillary exchange of transferrin and the rate of passage of plasma transferrin into the extravascular compartment of the intestinal mucosa were then measured in separate groups of rats. The rates of exchange were insufficient for transferrin to act as the carrier of iron at the rate at which it passes from intestinal cells to portal plasma after ingesting a dose of inorganic iron. Some specific binding of transferrin and cellular uptake of iron by intestinal mucosa was observed after the intravenous injection of transferrin labelled with 59Fe and 1251. It is concluded from these experiments that absorbed iron passes from intestinal cells to portal plasma largely in a low molecular weight form. The passage of plasma transferrin into the interstitial fluid of the intestinal mucosa and binding to mucosal cells probably functions primarily to supply iron to the cells and not to act as a carrier of iron from the cells.

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“…The physiology department has worked mainly on iron metabolism and gastrointestinal physiology (Kaldor & Ezekiel, 1962;Morgan, 1963Morgan, , 1966Redgrave & Simmonds, 1967).…”

Section: Foundation Of the Schoolmentioning

confidence: 99%

The promise of Perth

Joske

1970

Postgraduate Medical Journal

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Exchange of iron and transferrin across endothelial surfaces in the rat and rabbit

Cited by 18 publications

References 22 publications

Transferrin receptor expression during exponential and plateau phase growth of human tumour cells in culture

Transferrin receptor expression during exponential and plateau phase growth of human tumour cells in culture

The Role of Plasma Transferrin in Iron Absorption in the Rat

The promise of Perth

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