Iron disorders can mimic anything, so always test for them

Intestinal hephaestin potentiates iron absorption in weanling, adult, and pregnant mice under physiological conditions

Regulation of intestinal iron absorption is crucial to maintain body iron levels because humans have no regulated iron-excretory system. Elucidating molecular events that mediate intestinal iron transport is thus important for the development of therapeutic approaches to modify iron absorption in pathological states. The process of iron uptake into duodenal enterocytes is relatively well understood, but less is known about the functional coupling between the iron exporter ferroportin 1 and the basolateral membrane iron oxidase hephaestin (Heph). Initial characterization of intestine-specific Heph knockout (Heph^int) mice demonstrated that adult male mice were mildly iron deficient; however, the specific role of intestinal Heph has not been determined in weanling mice, in female mice, or during physiological states which stimulate iron absorption. Furthermore, because ferroportin 1-mediated iron export from some tissues (eg, liver) is impaired in the absence of the Heph homolog, ceruloplasmin, we hypothesized that Heph is rate limiting for intestinal iron absorption, especially when iron demands increase. Our experimental approach was to assess various physiological parameters and iron (⁵⁹Fe) absorption and tissue distribution in weanling, adult, and pregnant Heph^int mice (and controls) under physiological conditions and in adult Heph^int mice after dietary iron deprivation or acute hemolysis. Results demonstrate that intestinal Heph is essential for optimal iron transport in weanlings and adults of both sexes and during pregnancy, but not in adult mice with iron-deficiency or hemolytic anemia. Moreover, activation of unidentified, intestinal ferroxidases was noted, which may explain why intestinal Heph is not always required for optimal iron absorption.

Comparison of the Ames, Randox and Roche methods with the Synermed method for the determination of serum iron concentrations on nondialysis and dialysis specimens

OBJECTIVES

To evaluate the Ames, Randox, Roche, and Synermed methods for the measurement of serum iron and to investigate patterns of possibly discrepant results in dialysis patients.

METHODS

Assays were performed on the Cobas Fara II analyzer. Precision and accuracy studies were conducted; recovery studies were done by adding pooled serum from dialysis patients to an assayed human serum-based control. Patient comparisons included over 150 nondialysis patients and 30 dialysis patients.

RESULTS

For the Ames, Randox, Roche and Synermed methods, the between-run precision was less than 2.80% with the normal aqueous iron standard; 2.00, 2.70, 0.80, and 2.00% for the four methods with the high serum iron control, respectively, and less than 2.30% with the serum pool. Using a pooled serum from dialysis patients, between-run precision was higher with all four methods. With an abnormal assayed human serum-based control, accuracy was over 98% for the four methods. Recoveries were 121% for the Ames and Randox methods and 104-105% for the Roche and Synermed methods. Accuracy as assessed with Murex EQAS specimens ranged from 71 to 80%, 71 to 96%, 98 to 99.5%, and 42 to 50% for the four methods, respectively. For comparisons of the Ames, Randox, and Roche methods with the Synermed method, difference analyses revealed biases (SD) for nondialysis patients of 1.9 (2.7), 1.5 (3.3), and 1.8 (2.2) mumol/L, respectively; and for dialysis patients of 8.2 (13.3), 5.1 (5.4), and 1.4 (1.7) mumol/L. Standard linear regression analyses and correlation coefficients are also provided.

CONCLUSIONS

The Roche method was slightly more precise than the other methods. Using an abnormal assayed serum-based control, all methods showed good accuracy. Recovery studies with pooled serum from dialysis patients showed interferences with the Ames and Randox methods and good recovery with the Roche and Synermed methods. With the bovine serum-based Murex samples, all but the Roche method yielded some low results; the Synermed method has been reported to suffer from matrix problems with bovine serum albumin. Based on recovery studies and difference analyses, the Ames and Randox methods revealed discrepancies in iron results for samples from dialysis patients. The Roche and Synermed methods appeared to be suitable for measurement of serum iron in dialysis patients.

Trace elements in parenteral micronutrition

OBJECTIVE

To update some essential trace metals required in total parenteral nutrition.

CONCLUSION

Essential trace metals, chromium, copper, manganese, molybdenum, selenium, and zinc are added to parenteral fluids to prevent the development of deficiency syndromes. When possible, these metals should be monitored, even in patients on short-term total parenteral nutrition (TPN) to avoid deficiency or toxicity. Many of the nutrients or additives used in parenteral solutions may be contaminated with metals, such as aluminum or chromium. Such trace-metal monitoring becomes more critical in infants, and those on long-term TPN.

Quantitative determination of serum iron in human blood by high-performance capillary electrophoresis

A capillary electrophoretic (HPCE) method that can be used to quantitatively determine trace amounts of iron has been developed and applied to determine the iron level in human serum. After precipitation of serum proteins, Fe(III) in the serum is reduced to Fe(II) with hydroxylamine hydrochloride, and a stable Fe(II)-1,10-phenanthroline complex is formed by adding 1,10-phenanthroline to the supernatant containing 2.5 mM ammonium acetate-acetic acid at pH 5.0. The Fe(II)-1,10-phenanthroline complex, [Fe(C12H8N2)3]2+, has a very strong absorbance at 270 nm (with a molar absorptivity of approximately 9.2.10(4)). By measuring the absorbance of [Fe(C12H8N2)3]2+ at 270 nm, the iron level in human serum can be precisely quantified. The interference from copper, a major interference in serum, can be totally eliminated due to the complete separation of [Fe(C12H8N2)3]2+ and the Cu(II)-1,10-phenanthroline complex. In addition, other problems that usually occurred with conventional spectrophotometric methods, such as co-precipitation and occlusion of iron during sample pretreatment, are significantly minimized due to the ability to wash the precipitate and the higher detection sensitivity. With this method, a single drop (10 microliters) of serum would be sufficient to determine the serum iron concentration. The method is reliable, sensitive, rapid and reproducible. Thus it is highly suitable for use in the clinical laboratory.

The antioxidant and prooxidant activity of some B vitamins and vitamin-like compounds

The antioxidant and prooxidant properties of some B vitamins (BVIT) and vitamin-like compounds (VLC) that are commonly included in multivitamin preparations were investigated. Microsomal lipid peroxidation induced by FeCl3 and ascorbate was dose-dependently inhibited by pyridoxal and pantothenate but was stimulated by thiamin, pyridoxine and carnitine. Among the compounds tested, only pyridoxine and pyridoxal reacted, but rather poorly, with superoxide anions. All test compounds reacted with .OH with second-order rate constants comparable or higher than that for mannitol, as assayed using deoxyribose oxidation by a system containing EDTA-chelated Fe(III), H2O2 and ascorbate. When assayed in the absence of EDTA, pyridoxal showed increased inhibition of deoxyribose oxidation over that in the presence of EDTA, suggesting a potent ability of pyridoxal to bind and deactivate iron. Pantothenate, pyridoxine and myo-inositol appeared to equally inhibit deoxyribose oxidation both in the presence and absence of EDTA. The lack of inhibition on deoxyribose oxidation in the absence of EDTA by thiamin, carnitine and choline may suggest that the .OH-scavenging ability is equalled by the ability of the scavenger-iron complexes to form .OH or other redox active species. However, stimulation of lipid peroxidation by pyridoxine was unexplained and the effect was not attributed to reduction of Fe(III) to Fe(II). This study shows that the radical-scavenging ability of BVIT and VLC did not correlate with their effects on microsomal lipid peroxidation. Moreover, the stimulation of lipid peroxidation by thiamin, pyridoxine and carnitine suggests that supplementation of large amounts of these compounds may not be desirable.