Affiliation:
1. Zoophysiological Laboratory, The August Krogh Institute, University of Copenhagen, Denmark
2. King's College London, School of Health and Life Sciences, Franklin Wilkins Building, 150 Stamford Street, London, SE1 9NN, UK
Abstract
SUMMARYWaterborne iron accumulation by the gills of the zebrafish Danio rerio was assessed in ion-poor water. Branchial iron uptake, which comprises both the iron that has entered the gill cells and iron that is strongly bound to the epithelia, has high- and low-affinity components. At low nominal [Fe] (<40 nmol l-1) the high-affinity component demonstrated saturation kinetics, with an apparent Km of 5.9 nmol l-1 Fe and Vmax of 2.1 pmol g-1 h-1. Over a range of higher nominal [Fe] (40-200 nmol l-1), branchial uptake was linear. In the presence of 2μmol l-1 of the reducing agent dithiothreitol (DTT), branchial iron accumulation was significantly enhanced at [Fe]>15 nmol l-1. The proton pump inhibitor bafilomycin A significantly reduced iron uptake in the presence of DTT. On the basis of these observations we conclude that branchial iron uptake at low [Fe] shows characteristics similar to those of other iron-transporting epithelia, coupling an apical membrane ferric reductase to a Fe2+/H+ symporter. Zebrafish branchial iron transport at 18.6 nmol l-1 was inhibited by 200 nmol l-1 Cd2+. But, unlike other Fe2+/H+ symporters, iron uptake was not affected by other divalent metals (Co2+, Ni2+, Pb2+,Cu2+, Zn2+ and Mn2+). Zebrafish loaded with 59Fe from the water showed a loss of 7.9 pmol Fe g-1body mass over the first day and a further loss of 5.7 pmol Fe g-1body mass over the following 28 days. The depuration kinetics followed a two-component exponential model; for the short-lived component, t1/2=0.31 days, and for the long-lived component, t1/2=13.2 days. The daily iron loss by zebrafish can be compensated by iron uptake at exceedingly low water iron concentrations(uptake rate at 1.625 nmol l-1 Fe=0.425 pmol g-1h-1), demonstrating that uptake of iron from the water is potentially an important source of this nutritive metal in freshwater teleost fish.
Publisher
The Company of Biologists
Subject
Insect Science,Molecular Biology,Animal Science and Zoology,Aquatic Science,Physiology,Ecology, Evolution, Behavior and Systematics
Cited by
45 articles.
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