Species specificity of transferein binding,endocytosis and iron internalization by cultured chick myogenic cells |
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Authors: | L M Sorokin E H Morgan |
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Institution: | (1) Department of Physiology, University of Western Australia, 6009 Nedlands, Western Australia, Australia |
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Abstract: | Summary The ability of unlabelled heterologous transferrin to interact with transferrin receptors on developing chick myogenic cells was investigated by measuring their capacity to inhibit the surfacebinding and internalization of125I-and59Fe-labelled ovotransferrin. Transferrins from rat, rabbit, human, and a species of kangaroo (Macropus fuliginosus) were unable to inhibit either surfacebinding or internalization of labelled ovotransferrin even at concentrations ten times the molar concentration of the ovotransferrin. Transferrins isolated from the serum of a toad (Bufo marinus) and a lizard (Teliqua rugosa), when added at high concentrations, were found to reduce surface-binding of125I-Tf by 20–25% but did not inhibit internalization of either125I-Tf or59Fe. This suggests that the effects of toad and lizard transferrins are due to non-specific binding to the myogenic cells. In contrast, inhibition of both surface-binding and internalization of labelled ovotransferrin was found when myogenic cells were incubated in the presence of the homologous transferrin (ovotransferrin). The species-specificity of transferrin binding, endocytosis and iron internalization did not vary with the state of proliferation or differentiation of the myogenic cells. However, the intracellular iron utilization was found to differ between differentiating presumptive and terminally differentiated myotubes. Internalized59Fe was fractioned by gel filtration. In dividing and non-dividing presumptive myoblasts59Fe was found to elute in three peaks, two with elution volumes corresponding to ferritin and transferrin and one at greater elution volume than that of myoglobin. In myotubes the same fractions occurred, and in addition some59Fe was eluted at the same volume as myoglobin.Abbreviations
Tf-Fe
2
differic transferrin
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BSA
bovine serum albumin
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BSS
balanced salt solution
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MEM
Eagle's modified minimum essential medium
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MW
molecular weight
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BUdR
bromodeoxyuridine
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Ara-C
cytosine arabinoside |
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