In Vitro Cellular & Developmental Biology - Animal

, Volume 32, Issue 8, pp 486–495 | Cite as

Intermediate steps in cellular iron uptake from transferrin. II. A cytoplasmic pool of iron is released from cultured cells via temperature-dependent mechanical wounding

  • D. R. Richardson
  • L. Dickson
  • E. Baker
Cellular Models


A previous study described a cytoplasmic, transferrin (Tf)-free, iron (Fe) pool that was detected only when cells were mechanically detached from the culture substratum at 4°C, after initial incubation with59Fe-125I-Tf at 37°C (Richardson and Baker, 1992a). The release of this internalized59Fe could be markedly reduced if the cells were treated with proteases or incubated at 37°C prior to detachment. The present study was designed to characterize this Fe pool and understand the mechanism of its release. The results show that cellular59Fe release increased linearly as a function of preincubation time with59Fe-Tf subsequent to mechanical detachment at 4°C using a spatula. These data suggest that the59Fe released was largely composed of end product(s) and was not an “intermediate Fe pool.” When the Fe(II) chelator, dipyridyl (DP), was incubated with59Fe-Tf and the cells, it prevented the accumulation of59Fe that was released following mechanical detachment at 4°C. Other chelators had much less effect on the proportion of59Fe released. Examination of the59Fe released showed that after a 4-h preincubation with59Fe-Tf, approximately 50% of the59Fe was present in ferritin. These data indicate that mechanical detachment of cells at 4°C resulted in membrane disruptions that allow the release of high M, molecules. Moreover, electron microscopy studies showed that detachment of cells from the substratum at 4°C resulted in pronounced membrane damage. In contrast, when cells were detached at 37°C, or at 4°C after treatment with pronase, membrane damage was minimal or not apparent. These results may imply that temperature-dependent processes prevent the release of intracellular contents on membrane wounding, or alternatively, prevent wounding at 37°C. The evidence also indicates that caution is required when interpreting data from expriments where cells have been mechanically detached at 4°C.

Key words

mechanical wounding intracellular iron pools ferritin transferrin 


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Copyright information

© Society for in Vitro Biology 1996

Authors and Affiliations

  • D. R. Richardson
    • 1
    • 2
  • L. Dickson
    • 3
  • E. Baker
    • 3
  1. 1.Lady Davis Institute for Medical Research of the Sir Mortimer B. Davis-Jewish General HospitalMontréalCanada
  2. 2.Department of MedicineMcGill UniversityPerth
  3. 3.Department of PhysiologyUniversity of Western AustraliaPerth

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