MODULATION OF DUODENAL IRON UPTAKE BY HYPOXIA AND FASTING IN THE RAT

The effect of hypoxic exposure on in vitro duodenal Fe uptake kinetics was studied in tissue fragments from rats that were fed or fasted ove rnight before study. Hypoxic exposure was for 3 d at 0.5 atm and fasti ng was for the last 18-24 h before Fe uptake determinations. The non-p ermeable Fe2+ chelator 3-(2-pyridyl)-5,6-bis-(4-phenyl-sulphonic acid) -1,2,4-triazine (ferrozine), and medium deoxygenation inhibited uptake in all experimental groups. Ferrozine sensitivity and mucosal Fe3+ re ductase activity were greatest in hypoxic animals. Fe uptake was inhib ited by membrane depolarization only after fasting or hypoxic exposure of the rats. The data demonstrated that Fe uptake by rat duodenal fra gments involves at least two mechanisms: a membrane-potential-independ ent mechanism which is not responsive to hypoxia and a second mechanis m, induced by fasting or hypoxia, which is inhibited by membrane depol arization. Uptake is partially dependent on reduction of Fe3+ to Fe2and this is primarily associated with the second mechanism for uptake. These properties have been reported also in mouse and human Fe uptake , suggesting that the rat is a useful model for the study of basic mec hanisms of Fe absorption.