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Mechanisms involved in increased iron uptake across rat duodenal brush‐border membrane during hypoxia.
Author(s) -
O'Riordan D K,
Debnam E S,
Sharp P A,
Simpson R J,
Taylor E M,
Srai S K
Publication year - 1997
Publication title -
the journal of physiology
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.802
H-Index - 240
eISSN - 1469-7793
pISSN - 0022-3751
DOI - 10.1113/jphysiol.1997.sp022028
Subject(s) - enterocyte , brush border , hypoxia (environmental) , biophysics , chemistry , depolarization , hyperpolarization (physics) , membrane potential , medicine , endocrinology , biology , microbiology and biotechnology , small intestine , biochemistry , membrane , oxygen , vesicle , organic chemistry , nuclear magnetic resonance spectroscopy
1. Chronic hypoxia enhances intestinal iron transport but the cellular processes involved are poorly understood. In order to assess the effects of 3 days of hypoxia on iron uptake across the duodenal brush‐border membrane, we have measured the membrane potential difference (Vm) of villus‐attached enterocytes by direct microelectrode impalement and have used semi‐quantitative autoradiography to study changes in expression of iron uptake during enterocyte maturation. 2. Hypoxia increased duodenal Vm (‐57.7 vs. ‐49.3 mV, P < 0.001). Ion substitution experiments revealed that hyperpolarization was due, at least in part, to a reduction in brush‐border Na+ permeability. 3. Autoradiography revealed that hypoxia increased by 6‐fold the rate of iron accumulation during enterocyte transit along the lower villus and enhanced by 3‐fold the maximal accumulation of iron. Depolarization of the brush border, using a high‐K(+)‐containing buffer, caused a proportionally greater reduction in iron uptake in control compared with hypoxic tissue suggesting that the raised iron uptake is only partly driven by brush‐border hyperpolarization. 4. We conclude that hypoxia increases the expression of iron transport in duodenal brush‐border membrane and an enhanced electrical driving force may be involved in this response.