Non-haem Iron Concentration Research Articles

Haem-mediated protein oxidation affects water-holding capacity of beef during refrigerated storage.

Haem is considered to be a potential producer of meat oxidation and the effect of its mediated oxidation on the water holding capacity (WHC) of beef is not yet clear. This work investigated the interrelationships between haem, protein and lipid oxidation, and WHC in beef during refrigerated storage. The increase in juice loss during storage (p<0.05) indicates a reduction in WHC. Haem was oxidised, resulting in its structural disruption and an increase in the proportion of random coil in the protein secondary structures (p<0.05). Extractable haem iron content was decreased and non-haem iron content was increased (p<0.05), indicating the degradation of haem and the release of iron during storage. The levels of lipid and protein oxidation products significantly increased throughout the storage time (p<0.05). Furthermore, Spearman analysis verified significant correlations between these changes. In conclusion, these processes are mutually reinforcing and may exacerbate muscle juice loss.

N-nitrosodimethylamine reduction by Lactobacillus pentosus R3 in fermented cooked sausages

This study investigated the effects of Lactobacillus pentosus R3 on N-nitrosodimethylamine (NDMA) in the production and cooking of fermented sausages. L. pentosus significantly decreased the content of NDMA in fermented sausages, especially after the ripening and cooking steps (P < 0.05). Dimethylamine and carbonyl content, thiobarbituric acid reactive substances value, and content of non-haem iron of the sausages inoculated with L. pentosus were significantly lower than those of the control (P < 0.05). It means that L. pentosus may decrease NDMA content in the sausages through direct degradation, indirect reduction of its precursors, weakened oxidation, and a decrease in the non-haem iron content. In addition, the lower pH and water activity of the inoculated sample may also inhibit the formation of NDMA by improving the microbial quality of the sausages. Therefore, inoculating L. pentosus R3 into fermented cooked sausages is an effective way to reduce NDMA content.

After haemin treatment intracellular non-haem iron increases prior to haem oxygenase-1 induction: A study in human monocytic cell line THP-1

BackgroundIron overload is a major health concern for transfusion-dependent patients. Repeated transfusions result in the loading of large amounts of haem-derived iron on macrophages, in turn, inducing cell death. We previously demonstrated that haemin-induced cell death in human monocytic THP-1 cells is consistent with ferroptosis, an iron-dependent cell death regulation mechanism. However, direct measurement of iron after haemin treatment has not yet been conducted. In this study, we measured intracellular non-haem iron concentration and haem oxygenase levels after haemin treatment. Material and methodsHuman monocytic THP-1 cells were treated with haemin, and the cell lysate was prepared. Non-haem iron concentration of the cell lysate was measured using the Nitroso-PSAP method. Expression of haem oxygenase-1 (HO-1) and haem oxygenase-2 (HO-2) was quantified by western blotting. ResultsWe measured intracellular non-haem iron and the expression of haem oxygenases post-haemin treatment. Concentration of non-haem iron post-haemin treatment increased dependently with time and dose. HO-1 expression was detected 4 h after haemin treatment, whereas HO-2 expression was constitutive. DiscussionIncrease in non-haem iron prior to induction of HO-1 expression suggests the involvement of HO-2 in haem-induced cytotoxicity. (184 words)

Quercetin inhibits intestinal non-haem iron absorption by regulating iron metabolism genes in the tissues

PurposeThere is general agreement that some dietary polyphenols block non-haem iron uptake, but the mechanisms by which they achieve this action are poorly understood. Since the polyphenol quercetin is ingested daily in significant amounts, we have investigated the effect of quercetin on duodenal non-haem iron absorption in vivo, as well as its effect on factors known to be involved in systemic iron metabolism.MethodsRats were subject to gastric gavage and systemic quercetin administration. Treatments were followed with uptake studies using radiolabeled iron, serum iron and transferrin saturation measurements, LC-MS/MS analysis of quercetin metabolites in serum, determination of tissue non-haem iron content and analysis of gene expression of iron-related proteins.ResultsBoth oral and intraperitoneal (IP) quercetin caused serum and tissue iron depletion by two means, first by increasing mucosal iron uptake and inhibiting iron efflux from duodenal mucosa, and second by decreasing levels of duodenal DMT1, Dcytb and FPN. Additionally, IP quercetin induced highly significant increased liver expression of hepcidin, a hormone known to inhibit intestinal iron uptake.ConclusionsOral quercetin significantly inhibited iron absorption, while IP quercetin significantly affected iron-related genes. These results could lead to development of new effective ways of preventing and treating iron deficiency anaemia, the most widespread nutritional disorder in the world.

Inflammation neither increases hepatic hepcidin nor affects intestinal 59Fe-absorption in two murine models of bowel inflammation, hemizygous TNFΔARE/+ and homozygous IL-10−/− mice

Hepcidin-synthesis was reported to be stimulated by inflammation. In contrast, hepcidin synthesis was inhibited by TNFα and serum hepcidin was low. To elucidate these contradictions, we compare data on hepcidin expression, on iron absorption and homoeostasis and markers of inflammation between two murine models of intestinal inflammation and corresponding wild-types as determined by standard methods.In TNFΔARE/+ and IL-10−/−-mice hepatic hepcidin expression and protein content was significantly lower than in corresponding wild-types. However, 59Fe whole-body retention showed no difference between knock-outs and corresponding wild-types 7d after gavage, in neither strain. Compared to wild-types, body weight, hepatic non-haem iron content, hemoglobin and hematocrit were significantly decreased in TNFΔARE/+ mice, while erythropoiesis increased. These differences were not seen in IL-10−/− mice. Duodenal IL-6 and TNFα content increased significantly in TNFΔARE/+ mice, while ferritin-H decreased along with hepatic hepcidin expression, ferritin L, and non-haem iron. In IL-10−/− mice, these changes were less marked or missing for non-haem iron. Duodenal ferritin-L and ferroportin increased significantly, while HFE decreased.Our results corroborate the conflicting combination of low hepcidin with inflammation and without increased intestinal iron absorption. Speculating on underlying mechanism, decreased hepcidin may result from stimulated erythropoiesis. Unaltered intestinal iron-absorption may compromise between the stimulation by increased erythropoiesis and inhibition by local and systemic inflammation. The findings suggest intense interaction between counterproductive mechanisms and ask for further research.

Lipid oxidation and fishy odour in protein hydrolysate derived from Nile tilapia (Oreochromis niloticus) protein isolate as influenced by haemoglobin

Although protein isolates have been proven as a potent raw material for protein hydrolysate preparation, the fishy odour associated with lipid oxidation is still detected. The remaining haemoglobin (Hb) in protein isolates can effectively induce lipid oxidation, leading to the formation of fishy odour in the resulting hydrolysate. The aim of this study was to elucidate the impact of Hb with different forms, oxyhaemoglobin (oxy-Hb) and methaemoglobin (met-Hb), on lipid oxidation and the development of fishy odour during hydrolysis of protein isolates. During hydrolysis of protein isolate up to 120 min, non-haem iron content, peroxide value and thiobarbituric acid reactive substances slightly increased (P < 0.05). When oxy-Hb or met-Hb was incorporated, the marked increases in all parameters were observed, especially within the first 60 min of hydrolysis. The higher increases were obtained with the latter, suggesting that met-Hb was more pro-oxidative than oxy-Hb. However, no differences in degree of hydrolysis of all samples were observed (P > 0.05). The marked increases in the b*, ΔE*, ΔC* values, fishy odour/flavour and volatile compounds were also found in the resulting hydrolysate containing either oxy-Hb or met-Hb. Hb, particularly met-Hb, induced lipid oxidation and the development of a fishy odour/flavour in fish protein hydrolysate.

Effect of pretreatment on lipid oxidation and fishy odour development in protein hydrolysates from the muscle of Indian mackerel

Impact of different pretreatments on chemical compositions of Indian mackerel mince was studied. Mince prepared using washing/membrane removal/alkaline solubilisation process (W–MR–Al) contained the lowest remaining myoglobin and haem iron content and also showed the lowest total lipid and phospholipid contents. When mince and W–MR–Al were hydrolysed using Alcalase for up to 120min, a higher degree of hydrolysis (DH) was found in W–MR–Al after 30min of hydrolysis. Furthermore, hydrolysate from W–MR–Al had lower peroxide value (PV), thiobarbituric acid reactive substances (TBARS) and non-haem iron content throughout hydrolysis period (P<0.05). When hydrolysate powder produced from mince and W–MR–Al (0–0.3%w/v) were fortified in milk, the former resulted in the lower likeness score (P<0.05) at all levels used. The addition of the latter, for up to 0.2%, had no effect on likeness of all attributes, compared with milk without fortification (P>0.05). Therefore, the appropriate pretreatment of mince yielded hydrolysate with lower fishy odour.

Requirements of non-haem iron and haem iron in the nematode Caenorhabditis elegans

AbstractBoth non-haem iron (iron salt) and haem iron (cytochrome c) are components of the Caenorhabditis elegans Maintenance Medium (CeMM). However, the quantitative requirements of non-haem iron and its relationship with haem iron were unknown. A basal medium was prepared with both non-haem iron and haem iron eliminated from the CeMM. After being pre-cultured in this basal medium, C. elegans were inoculated into a 3 × 5 factorial design of experimental media, consisting of five levels of non-haem iron (0, 0.0672, 0.336, 8.40 and 210 μg ml–1) and three levels of cytochrome c (0, 50.0 and 500 μg ml–1). The population growth of C. elegans in various experimental media was counted at day 28, and the iron uptake (ng (1000 nematodes)–1) and percentage iron absorption (total iron in nematode tissue/total iron in original media) of the nematodes were analysed by atomic absorption spectrophotometry (AAS). At 0 μg ml–1 iron and 0 μg ml–1 cytochrome c, the population growth (2530±220 nematodes ml–1) was very poor. At 0 μg ml –1 cytochrome c, as iron level increased to 8.40 μg ml–1, the nematode population increased to 5980±530 nematodes ml–1. At 0 μg ml–1 iron, as cytochrome c level increased from 0 to 500 μg ml–1, the population growth was greatly increased from 2530±220 nematodes ml–1 to 45 900±3600 nematodes ml–1. Under the experimental conditions, the highest population growth (258 000±9000 nematodes ml–1) was achieved at 8.40 μg ml–1 iron and 500 μg ml–1 cytochrome c, suggesting an additive requirement of non-haem and haem iron. As the concentration of iron further increased from 8.40 to 210 μg ml–1, significant declines in nematode population were observed, indicating iron toxicity. Based on the Atomic Absorption analysis, the iron uptake by C. elegans increased when either non-haem or haem iron concentration increased in the media. At 0 μg ml–1 cytochrome c, the percentage iron absorption decreased from 7.39 to 0.118% with the increase of iron concentration (0-210 μg ml–1) in the media. This observation was in accordance with the 'mucosal block' theory. At 50.0 and 500 μg ml–1 cytochrome c, the percentage iron absorption greatly increased, and percentage iron absorption reached a maximum of 85.9% when media contained 0.336 μg ml–1 iron and 50.0 μg ml–1 cytochrome c, indicating an optimal percentage iron absorption in C. elegans.

Preventive effect of tannic acid in combination with modified atmospheric packaging on the quality losses of the refrigerated ground beef

Chemical, microbiological and sensorial changes of ground beef treated without and with tannic acid (200 mg/kg) and stored in air and under modified atmosphere packaging (MAP) (80%O 2/20%CO 2 or 10%O 2/20%CO 2/70%N 2) were monitored during 15 days of storage at 4 °C. During the storage, samples treated with tannic acid and kept under all packaging conditions contained lower peroxide value (PV) and thiobarbituric acid-reactive substances (TBARS) with coincidental lower non-haem iron content, compared with non-treated counterparts ( P < 0.05). The sample packed in high oxygen MAP treated without and with tannic acid had the higher oxymyoglobin and a * values and received the higher likeness scores for colour, whereas the samples stored in air and under low oxygen MAP showed the lower values, regardless of tannic acid treatment. After 15 days of storage, myosin heavy chain (MHC) and actin of all tannic acid treated samples underwent less degradation than those without tannic acid treatment for all packaging conditions. Degradation of MHC was more pronounced in samples kept under MAP with high oxygen. Psychrophilic bacterial count (PBC) of all tannic acid treated samples was lower, compared with that of non-treated samples ( P < 0.05), irrespective of packaging condition. Therefore, tannic acid treated samples stored under high oxygen MAP could maintain the red colour and retard lipid oxidation and microbial growth of ground beef during refrigerated storage.

Synergistic effect of tannic acid and modified atmospheric packaging on the prevention of lipid oxidation and quality losses of refrigerated striped catfish slices

Abstract Chemical, microbiological and sensorial changes of striped catfish ( Pangasius hypophthalmus ) slices treated without and with tannic acid (100 and 200 mg/kg) were determined during 15 days of storage at 4 °C in air and under modified atmospheric packaging (MAP, 60% N 2 /35% CO 2 /5% O 2 ). The slices consisted of 9.2 g lipid/100 g and the lipid contained 64.55% unsaturated fatty acids and 33.87% saturated fatty acids. During the storage, the sample treated with 200 mg/kg tannic acid and stored under MAP (M 2 ) had the lowest peroxide value (PV) and thiobarbituric acid-reactive substances (TBARS) with the coincidental lowest non-haem iron content, indicating the retarded lipid oxidation. Fourier transform infrared (FTIR) spectra indicated the formation of primary oxidation products and free fatty acids in M 2 sample after 15 days. Conversely, these compounds were found at lower contents in the control samples kept in air without tannic acid treatment (A 0 ), suggesting that the deterioration was more advanced. Myosin heavy chain of A 0 was degraded by 17.85% after 15 days of storage, whereas no change was noticeable in M 2, compared with the fresh sample (F). Based on microbiological acceptability limit (10 7 cfu/g), the shelf-life of A 0 and M 2 was estimated to be 3 and 15 days, respectively. M 2 had the acceptable scores for all sensory attributes up to 15 days, while A 0 was acceptable when stored for 9 days. Therefore, tannic acid exhibited a synergistic effect with MAP on retarding lipid oxidation and microbial growth, thereby increasing the shelf-life of striped catfish slices during refrigerated storage.

Iron absorption and distribution in TNF ΔARE/+ mice, a model of chronic inflammation

Hemizygous TNF ΔARE/+ mice are a murine model for chronic inflammation. We utilized these animals to study iron-kinetics and corresponding protein expression in an iron-deficient and iron-adequate setting. 59Fe-absorption was determined in ligated duodenal loops in vivo. Whole body distribution of i.v. injected 59Fe was analysed, and the organ specific expression of ferroportin, transferrin receptor-1, hepcidin and duodenal DMT-1 was quantified by real-time PCR and Western blotting. Duodenal 59Fe-lumen-to-body transport was not affected by the genotype. Duodenal 59Fe-retention was increased in TNF ΔARE/+ mice, suggesting higher 59Fe-losses with defoliated enterocytes. Iron-deficiency increased duodenal 59Fe-lumen-to-body transport, and higher duodenal 59Fe-tissue retention went along with higher duodenal DMT-1, ferroportin, and liver hepcidin expression. TNF ΔARE/+ mice significantly increase their 59Fe-content in inflamed joints and ilea, and correspondingly reduce splenic 59Fe-content. Leukocyte infiltrations in the joints suggest a substantial shift of iron-loaded RES cells to inflamed tissues as the underlying mechanism. This finding was paralleled by increased non-haem iron content in joints and reduced haemoglobin and haematocrit concentrations in TNF ΔARE/+ mice. In conclusion, erythropoiesis in inflamed TNF ΔARE/+ mice could be iron-limited due to losses with exfoliated iron-loaded enterocytes and/or to increased iron-retention in RES cells that shift from the spleen to inflamed tissues.

The use of skin Fe levels as a surrogate marker for organ Felevels, to monitor treatment in cases of iron overload

A system based on the detection of K-shell x-ray fluorescence (XRF) has been used toinvestigate whether a correlation exists between the concentration of iron inthe skin and the concentration of iron in the liver, as the degree of ironloading increases. The motivation behind this work is to develop anon-invasive method of determining the extent of the body's iron stores viameasurements on the skin, in order to monitor the efficacy of chelationtherapy administered to patients with β-thalassaemia. Sprague-Dawleyrats were iron loaded via injections of iron dextran and subsequently treatedwith the iron chelator CP94. The non-haem iron concentrations of the liver,heart and spleen were determined using bathophenanthroline sulphonate as thechromogen reagent. Samples of abdominal skin were taken and the ironconcentrations determined using XRF. A strong correlation between the skiniron concentration and the liver iron concentration has been demonstrated(R2 = 0.86). Similar correlations exist for the heart and the spleen. Theseresults show that this method holds great potential as a tool in the diagnosisand treatment of hereditary haemochromatosis and β-thalassaemia.

Iron overload in urban Africans in the 1990s

BACKGROUNDIn a previously described model, heterozygotes for an African iron loading locus develop iron overload only when dietary iron is high, but homozygotes may do so with normal dietary iron....

Iron proteins of duodenal enterocytes isolated from mice with genetically and experimentally altered iron metabolism.

The molecular basis for the control of iron absorption by the duodenum remains unknown: however, ferritin (Ft) and the iron status of enterocytes have been suggested as regulatory factors. We determined the iron and Ft status of duodenal enterocytes from mice with hypotransferrinaemia, a genetic defect leading to greatly enhanced iron absorption, and for comparison we also investigated mice with experimentally-altered iron absorption. Duodenal enterocytes were isolated and analysed for Ft and non-haem iron content and for transferrin binding (as a measure of transferrin receptor activity). RNA was extracted from the duodenal mucosa and examined for transferrin receptor and H- and L-Ft mRNA levels by Northern hybridization analysis. Ft levels were elevated in enterocytes of hypotransferrinaemic mice, similar to that seen in iron dextran-injected mice of the CD1-strain. Enterocyte Ft levels were reduced in mice fed a diet diminished in iron, but unchanged in hypoxic mice enterocytes. Enterocytes of hypotransferrinaemic mice had normal non-haem iron levels and transferrin binding; however, enterocytes from CD-1 mice fed a low iron diet had increased transferrin binding and a decreased non-haem iron content. Duodenal mRNA levels for transferrin receptor and H-Ft were unchanged in hypotransferrinaemic mice, whereas L-Ft was increased. We conclude from the Ft and non-haem iron contents and transferrin binding that duodenal enterocytes from hypotransferrinaemic mice are not simply iron deficient, leading to increased expression of iron carriers proteins. Duodenal iron absorption can be enhanced in mice even when enterocyte Ft levels are raised or unchanged, suggesting that iron absorption is regulated by developmentally programmed expression of iron transporters by enterocytes.

Desferioxamine increases iron depletion and apoptosis induced by ara-C of human myeloid leukaemic cells.

We investigated whether changes in iron metabolism and the transferrin receptor (TRF-R) expression were involved in the antileukaemic effects of arabinoside cytosine (ara-C). Treatment with 100 nM ara-C for 48h reduced thymidine uptake and increased the surface expression of the TRF-R on leukaemic blasts derived from 13/16 (81%) patients and on the HL-60 and U-937 cell lines. Whereas intracellular non-haem iron was strongly depleted 24 h after ara-C addition, TRF-R up-regulation and recovery of intracellular non-haem iron concentration occurred together after a longer exposure of the cultured cells to the drug. Since iron is an essential regulator of cell proliferation we have evaluated the effects of the combination between ara-C and the iron chelator desferioxamine (DSF) on the growth of HL-60 and U-937 cells. We found that desferioxamine strongly potentiated the effects of ara-C on leukaemic cell growth inhibition and apoptosis. This is the first report of a positive interaction between ara-C and an iron chelator in terms of antileukaemic effects.

Iron loading of isolated rat hepatocytes inhibits asialoglycoprotein receptor dynamics and induces formation of rat hepatic lectin-1 [correction of leptin-1] (RHL-1) oligomers.

The major subunit [rat hepatic lectin-1 (RHL-1)] of the asialoglycoprotein (ASGP) receptor mediates endocytosis of the iron-binding protein lactoferrin (Lf) by isolated rat hepatocytes, yet iron loading of cultured adult rat hepatocytes increases the binding and endocytosis of Lf while greatly inhibiting the uptake of desialylated ligand. In the present study, we determined whether the iron-induced Lf-binding site is RHL-1 and examined the nature of the iron-induced block in ASGP receptor endocytic function. Isolated rat hepatocytes increased their non-haem iron content from 70 to 470 p.p. b. following incubation with ferric ammonium citrate (<=100 microgram/ml). These conditions blocked internalization of 125I-asialo-orosomucoid (ASOR) by approximately 90% but increased 125I-Lf endocytosis by 40%. ASOR and anti-RHL-1 sera blocked the binding and endocytosis of 125I-Lf on control cells but not on iron-loaded cells, indicating that the iron-induced Lf-binding site on hepatocytes is not RHL-1. Iron-loading of hepatocytes in the presence or absence of excess ASOR did not significantly alter the number of active ASGP receptors on the cell surface. In contrast, iron-loading decreased the number of active intracellular receptors by 40% and blocked the uptake of 125I-ASOR prebound to the cells by approximately 80%. Under these conditions, we found an iron-dependent evolution of 88 and 140 kDa RHL-1-containing, beta-mercaptoethanol-sensitive multimers that constituted up to 34 and 23%, respectively, of total immunodetectable RHL-1. We propose that iron-induced formation of cystinyl-linked RHL-1-containing multimers inhibits ASGP receptor movement between cell surface and interior and disrupts acylation of intracellular receptors.

Age-related storage of iron in the liver of horses.

The non-haem iron concentration was estimated in post-mortem liver samples from 51 horses (age range 1-25 years). Two were normal and 49 had been suffering from conditions that were not expected to have had long-term effects on iron metabolism. Muscle samples (splenius and biceps femoris) from 23 of these horses were also analysed. There was a highly significant age-related increase in the non-haem iron concentration in the liver (r = 0.635, p < 0.001), but not in the muscles, in which the iron concentration was much lower than in the liver.

The effects of heating and chemical treatment on the haem and non-haem iron content of heat-induced porcine blood curd

The effect of heating temperature (40–80°C), time (0–50 min), additions of ascorbic acid (0–5 g litre−1) and sodium nitrite (0–200 mg litre−1) on total, non-haem and haem iron of heat-induced porcine blood curd (a famous edible blood food in Taiwan) was investigated. The results show that non-haem iron content increased significantly (P < 0.05) when heated at above 55°C and was enhanced linearly (r = 0.96) with heating time at 80°C, while haem iron decreased relatively. In addition, a non-haem iron increase was observed in ascorbic acid, the maximum found with treatment at 4 g litre−1. On the contrary, haem iron content increased with the presence of sodium nitrite and there was a significant change with addition above 50 mg litre−1.

Iron absorption by hypotransferrinaemic mice

Iron absorption rates by homozygous and wild-type mice from a hypotransferrinaemic mouse colony were examined with in vivo tied-off duodenal segments and in vitro incubated duodenal fragments. Enhanced initial rates of mucosal uptake and carcass transfer by homozygotes, compared to wild-types, were observed. The changes in vivo and in in vitro uptake kinetics resemble changes seen in iron deficient or hypoxic mice, suggesting that the liver iron loading shown by homozygotes is due to a failure of the normal mechanism for regulation of iron absorption. In vivo mucosal uptake and carcass transfer of radioiron showed an inverse correlation with liver non-haem iron content in homozygous hypotransferrinaemic mice, suggesting that some degree of control of absorption, albeit at markedly reduced sensitivity, can operate in these mice. No correlation between haemoglobin level and iron absorption was observed in homozygous hypotransferrinaemic mice, suggesting that this regulator of iron absorption does not function in these mice. The precise pathogenic mechanism of the enhanced iron absorption in hypotransferrinaemia remains to be determined. Mucosal transferrin levels were found to parallel serum transferrin levels in homozygotes, heterozygotes and wild-type mice. This supports previous suggestions that mucosal transferrin is derived from plasma transferrin and that the enhancement of iron absorption, by physiological mechanisms, does not require the presence of mucosal transferrin.

An increase in the concentration of hepatic iron during the metamorphosis of the lamprey Geotria australis is accompanied by increased superoxide dismutase activity

The concentration of total non-haem iron and its ferritin iron component, and the activity of the enzyme superoxide dismutase (SOD), were measured in the livers of ammocoetes, metamorphosing animals (stages 1-7) and recently metamorphosed downstream migrants of the lamprey Geotria australis. Total non-haem iron in the liver rose significantly from 0.15-0.55 μg.mg wet weight(-1) in ammocoetes and metamorphosing stages 1-3 to 2.2-2.9 μg.mg(-1) in stages 5-7 and to 8.8 μg.mg(-1) in downstream migrants. The comparable values for ferritin iron were 0.06-0.26, 1.4-2.0, and 5.3 μg.mg(-1). Superoxide dismutase activity fell sharply from 0.39 μg.mg(-1) in large ammocoetes to between 0.07 μg.mg(-1) in stage 1 and 0.15 μg.mg(-1) in stage 6, before rising significantly to 0.26 μg.mg(-1) in stage 7 and 0.35 μg.mg(-1) in downstream migrants. The sharp fall in SOD activity at the beginning of metamorphosis is assumed to be related to the marked decline in plasma iron which occurs at the onset of this non-trophic phase in the life cycle. It is proposed that the subsequent increase in SOD activity in the liver of G. australis with increasing iron represents a mechanism aimed at reducing the potentially toxic effects of iron accumulation. This view is consistent with the significant and positive correlation found between both total non-haem and ferritin iron and SOD activity in the liver of non-trophic animals.