Non-transferrin-bound iron species in the serum of hypotransferrinaemic mice.

Serum from homozygous hypotransferrinaemic mice (a mixed group of males and females, aged 6-8 wk) was found to contain low levels of iron (mean 0.9 +/- 0.5 microM (SEM, n = 4), as assayed by conventional serum iron assays. Similarly, low levels of non-transferrin-bound iron were determined with a nitrilotriacetate chelation assay (1.3 +/- 0.4 microM, n = 4) (Singh, S., Hider, R.C. and Porter, J.B. (1990) Analytical Biochemistry 186, 320-323). Mononuclear Fe (citrate) was undectable by electron paramagnetic resonance spectroscopy (EPR). Significantly larger quantities of iron (16 +/- 5 microM, n = 8) were detected by the bleomycin assay (Gutteridge, J.M.C., Rowley, D.A. and Halliwell, B. (1981) Biochemical Journal 199, 263-265), while non-haem iron assay or atomic absorption spectrophotometry revealed up to 96 microM iron. Haemoglobin iron was detectable at approximately 10 microM by spectrophotometry. Ferri-haem was undetectable by EPR spectroscopy. Serum ferritin levels of 641 +/- 128 micrograms/l (n = 14) in hypotransferrinaemic mice (wild-types 44 +/- 6 micrograms/l, n = 14) were observed and these cannot account for the non-transferrin-bound iron. Hypotransferrinaemic mouse serum therefore contains large quantities of non-transferrin-bound iron which is unreactive in some assays used to detect such iron in human iron overload. Fractionation by Sephadex G200 chromatography revealed three distinct species with apparent molecular weights of > or = 150 kDa, 40-80 kDa and 1-5 kDa. The iron may be distinguished from known extracellular iron proteins and haem-proteins by its availability to hot acid extractions.     

Iron metabolism in Trypanosoma lewisi infection: serum iron and serum iron-binding capacity.

Progressive changes in iron levels, total iron binding capacity and hematocrit values in sera of rats infected with Trypanosoma lewisi are described. The host dietary group were: (1) complete or full complement; (2) iron-deficient, and (3) pair-fed or calorically restricted. The hematocrit values of T. lewisi-infected rats given the various diets were not significantly different from those of the controls. The decrease in total iron binding capacity (TIBC) of rats inoculated with T. lewisi and fed complete and pair-fed diets ranged up to 15% over uninfected controls. TIBC levels in rats fed an iron-deficient diet and inoculated with T. lewisi ranged up to 32% over uninfected controls. TIBC levels of deficient infected rats were significantly different from the controls from day 90 to infection to the end of the observation period. Serum iron (SI) values of non-infected rats regardless of dietary regimen showed significantly higher values than T. lewisi-infected animals between days 95 and 120. The average SI value, for this period, in adequately fed control rats was 204 +/- 7 microgram/100 ml as compared to 172 +/- 5 microgram/100 for trypanosome-infected rats. SI levels of rats on a pair-fed diet and infected with T. lewisi decreased to 17% over uninfected controls. SI levels of animals on an iron-deficient diet and infected with T. lewisi decreased up to 76% over uninfected controls.     

EPR study of serum ceruloplasmin and iron transferrin in myocardial infarction.

Electron paramagnetic resonance (EPR) analysis of frozen serum from myocardial infarction patients has been conducted. Signal at g=4.3 was found definitively attributable to iron(III)-transferrin complex. Imcrease of serum ceruloplasmin as compared to normal was confirmed, with a concomitant decrease of iron-transferrin content. A mechanism for such correlated variation is hypothesized.     

Removal of iron from diferric rabbit serum transferrin by rabbit reticulocytes.

When radioiron-labelled transferrin with 55Fe located predominantly in the N-terminal iron-binding site and 59Fe predominantly in the C-terminal iron-binding site was incubated with rabbit reticulocytes, both radioisotopes of iron were removed at similar rates. Electrophoresis of transferrin samples taken during the course of an incubation, in polyacrylamide gels containing 6 M-urea, showed that iron was removed in a pairwise fashion, giving rise to iron-free transferrin.     

Assessment of iron stores in inflammation by assay of serum ferritin concentrations.

A serum ferritin concentration of below 15 microgram/l is accepted as indicating diminished iron reserves in an otherwise normal person. In patients with inflammatory disease this lower limit of normality may be inappropriate as inflammation may directly stimulate the production of ferritin protein. Results obtained in a survey of 150 patients with early inflammatory joint disease suggest that a ferritin concentration of 55 microgram/l is a more appropriate lower limit of normality.     

Ferritin in bone marrow and serum in iron deficiency and iron overload

Nonheme iron and ferritin in the bone marrow and serum ferritin was investigated in patients with iron deficiency anaemia or iron overload. As controls served patients without any disturbance of the iron metabolism. There is a precise correlation between the nonheme iron and ferritin in the bone marrow of patients with and without disturbance of iron metabolism. A correlation was also found between the ferritin in the bone marrow and the serum. Nonheme iron and ferritin in the bone marrow and serum ferritin was decreased in patients with iron deficiency anaemia. Conversely, the same parameters were increased in patients with iron overload.     

Effect of exercise-induced hyperthermia on serum iron concentration

Serum iron levels have been shown to decline both with fever and with strenuous exercise, leading to the supposition that the decrease might be the result of a rise in core body temperature. To evaluate this hypothesis, the serum iron response to an exercise-induced 1.5°C rise in core body temperature was measured. To increase core temperature, five females and two males exercised in an environmental chamber heated to 41°C with a relative humidity of 40%. Blood samples were taken before exercise and immediately after body temperature increased approximately 1.5°C. Blood was also collected 1 h, 6 h, and 24 h postexercise. Results showed that the core body temperature significantly increased (p<0.001) from a mean baseline value of 36.5±0.1°C to 38.1±0.1°C following exercise. A one-way repeated measures analysis of variance was used to examine the effect of increased core body temperature on serum iron levels over the five time periods: preexercise, immediate postexercise, and 1 h, 6 h, and 24 h postexercise. The results indicated that there were no significant differences in serum iron levels among time periods. This suggests that the previously reported depression of serum iron levels that occurs with fever and after prolonged exercise is not the result of hyperthermia. Rather, the change in serum iron occurs in response to biological or physiological stressors, such as bacterial infection, muscle damage, or unusual trauma. Further studies are needed to explicate the mechanisms responsible for these changes.     

Determination of iron in blood serum using flow injection with luminol chemiluminescence detection.

A simple and rapid fl ow injection method is reported for the determination of iron in blood serum after acid digestion with HNO3 and HClO4, based on luminol CL detection in the absence of added oxidant. The detection limit (3 s) was 1.0 nmol/L with a sample throughput of 120/h. The calibration graph was linear over the range 0.001-1.0 micromol/L (r2 = 0.9974), with relative standard deviations (RSD) (n = 4) in the range 3.2-5%. The effect of interfering cations (Ca(II), Mg(II), Cu(II), Cd(II), Pb(II), Mn(II), Zn(II), Ni(II), Co(II) and Fe(III)) and anions (Cl-, SO4(2-), HCO3-, NO3-, NO2-) were studied using a luminol CL system for Fe(II) determination. The method was applied to normal blood serum and the results (1.32 +/- 0.08-1.74 +/- 0.05 mg/L) were compared with those from a spectrophotometric reference method (1.34 +/- 0.06-1.80 +/- 0.10 mg/L), which agree fairly well with the overall reference range in blood.     

Oral administration of lactoferrin increases hemoglobin and total serum iron in pregnant women.

Iron deficiency anemia (IDA) during pregnancy continues to be of world-wide concern. IDA is a risk factor for preterm delivery and subsequent low birth weight, and possibly for poor neonatal health. Iron supplementation in pregnancy is a widely recommended practice, yet intervention programs have met with many controversies. In our study, 300 women at different trimesters of pregnancy were enrolled in a trial of oral administration of ferrous sulfate (520 mg once a day) or 30% iron-saturated bovine lactoferrin (bLf) (100 mg twice a day). Pregnant women refusing treatment represented the control group. In this group hemoglobin and total serum iron values measured after 30 d without treatment decreased significantly, especially in women at 18-31 weeks of pregnancy. In contrast, after 30 d of oral administration of bLf, hemoglobin and total serum iron values increased and to a greater extent than those observed in women treated orally for 30 d with ferrous sulfate, independently of the trimester of pregnancy. Unlike ferrous sulfate, bLf did not result in any side effects. These findings lead us to hypothesize that lactoferrin could influence iron homeostasis directly or through other proteins involved in iron transport out of the intestinal cells into the blood.     

Glucose acts as a regulator of serum iron by increasing serum hepcidin concentrations

Mutual clinical and molecular interactions between iron and glucose metabolism have been reported. We aimed to investigate a potential effect of glucose on iron homeostasis. We found that serum iron concentrations gradually decreased over 180 min after the administration of 75 g of glucose from 109.8±45.4 mg/L to 94.4±40.4 mg/L (P<.001; N= 40) but remained unchanged in control subjects receiving tap water (N= 21). Serum hepcidin, the key iron regulatory hormone which is mainly derived from hepatocytes but also expressed in pancreatic β-cells, increased within 120 min after glucose ingestion from 19.7±9.9 nmol/L to 31.4±21.0 nmol/L (P<.001). In cell culture, glucose induced the secretion of hepcidin and insulin into the supernatant of INS-1E cultures, but did not change the amount of hepcidin detectable in the hepatocyte cell culture HepG2. We additionally confirmed the expression of hepcidin in a human islet cell preparation. These results suggest that glucose acts as a regulator of serum iron concentrations, most likely by triggering the release of hepcidin from β-cells.