Characterization of a human plasma membrane heme transporter in intestinal and hepatocyte cell lines

M. T. Worthington, Steven Cohn, S. K. Miller, R. Q. Luo, C. L. Berg

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70 Scopus citations

Abstract

Heme is the most bio-available form of dietary iron and a component of many cellular proteins. Controversy exists as to whether heme uptake occurs via specific transport mechanisms or passive diffusion. The aims of this study were to quantify cellular heme uptake with a fluorescent heme analog and to determine whether heme uptake is mediated by a heme transporter in intestinal and hepatic cell lines. A zinc-substituted porphyrin, zinc mesoporphyrin (ZnMP), was validated as a heme homolog in uptake studies of intestinal (Caco-2, I-407) and hepatic (HepG2) cell lines. Uptake experiments to determine time dependence, heme inhibition, concentration dependence, temperature dependence, and response to the heme synthesis inhibitor succinylacetone were performed. Fluorescence microscope images were used to quantify uptake and determine the cellular localization of ZnMP; ZnMP uptake was seen in intestinal and hepatic cell lines, with cytoplasmic uptake and nuclear sparing. Uptake was dose- and temperature dependent, inhibited by heme competition, and saturated over time. Preincubation with succinylacetone augmented uptake, with an increased initial uptake rate. These findings establish a new method for quantifying heme uptake in individual cells and provide strong evidence that this uptake is a regulated, carrier-mediated process.

Original languageEnglish (US)
JournalAmerican Journal of Physiology - Gastrointestinal and Liver Physiology
Volume280
Issue number6 43-6
StatePublished - Jul 3 2001
Externally publishedYes

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Keywords

  • Iron
  • Micronutrients
  • Porphyrin
  • Succinylacetone
  • Trace elements
  • Zinc

ASJC Scopus subject areas

  • Gastroenterology
  • Physiology
  • Physiology (medical)

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