A micromethod for the determination of iron and total iron-binding capacity in intraocular fluids and plasma using electrothermal atomic absorption spectroscopy

McGahan, M.C.; Fleisher, Lloyd N.

doi:10.1016/0003-2697(86)90271-x

Cited by 27 publications

(12 citation statements)

References 14 publications

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“…Previously, McGahan and Fleisher (1986) had provided for the first time simultaneous values for TI, TIBC and TIBC % saturation in blood plasma and intraocular fluids of several animal species (dog, cat, pony, pig and rabbit) using an electrothermal atomic absorption spectroscopic (EAAS) microprocedure for the determination of iron.…”

Section: The Lensmentioning

confidence: 99%

Iron, the retina and the lens: A focused review

García-Castiñeiras

2010

Experimental Eye Research

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This review is focused on iron metabolism in the retina and in the lens and its relation to their respective age-related pathologies, macular degeneration (AMD) and cataract (ARC). Several aspects of iron homeostasis are considered first in the retina and second in the lens, paying particular attention to the transport of iron through the blood-retinal barrier and through the lens epithelial cell barrier, to the immunochemistry of iron-related proteins and their expression in both the retina and the lens, and to the nature of the photochemical damage caused by UV light on both tissues. A comparative overview of some iron related parameters (total iron, transferrin (Tf), transferrin saturation and total iron binding capacity), in plasma and ocular tissues and fluids of three animal species is also presented. Based on results selected from the literature reviewed, and our own results, a scheme for the overall circulation of iron within and out of the eye is proposed, in which, (i) iron is pumped from the retina to the vitreous body by a ferroportin/ferroxidase-mediated process at the endfeet of Müller cells, (ii) vitreal Tf binds this iron and the complex diffuses towards the lens, (iii) the iron/Tf complex is incorporated into the lens extracellular space probably at the lens equator and moves to the epithelial-fiber interface, (iv) upon interaction with Tf receptors of the apical pole of lens epithelial cells, the iron/Tf complex is endocytosed and iron is exported as Fe(3+) by a ferroportin/ferroxidase-mediated process taking place at the basal pole of the epithelial cells, and (v) Fe(3+) is bound to aqueous humor Tf and drained with the aqueous humor into systemic blood circulation for recycling. The proposed scheme represents an example of close cooperation between the retina and the lens to maintain a constant flow of iron within the eye that provides an adequate supply of iron to ocular tissues and secures the systemic recycling of this element. It does not discount the existence of additional ways for iron to leave the eye through the blood-retinal barrier. In this review both AMD and ARC are recognized as multifactorial diseases with an important photoxidative component, and exhibiting a remarkable similitude of altered local iron metabolism. The epidemiological relationship between ARC and ferropenic anemia is explained on the basis that hepcidin, the hormone responsible for the anemia of chronic inflammation, could paradoxically cause intracellular iron overload in the lens by interfering with the proposed ferroportin/ferroxidase-mediated export of iron at the basal side of the anterior lens epithelium. Other authors have suggested that a similar situation is created in the retina in the case of AMD.

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Section: The Lensmentioning

confidence: 99%

Iron, the retina and the lens: A focused review

García-Castiñeiras

2010

Experimental Eye Research

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“…Elevated content of cytosolic iron would increase its deposition into ferritin, and via a negative feedback mechanism, would limit iron uptake by Tf/TfR1. However, vitreous humor itself has a low iron content, 21 and its effects were the same when LEC were treated in media supplemented with 10% serum or without serum supplementation. We hypothesized that vitreous humor changes intracellular trafficking of iron, making it more available for the iron responsive protein/iron responsive element (IRP/IRE) regulatory system rather than increasing its uptake.…”

Section: Discussionmentioning

confidence: 96%

“…17–20 Vitreous humors of various species have low iron levels compared to plasma (2.4%–4.5% of plasma levels). 21 Under physiological conditions, low iron content and relatively high levels of unsaturated iron-binding capacity of Tf limit non–Tf-bound iron (NTBI) uptake by surrounding tissues. However, under pathological conditions such as vitreous hemorrhage, excess iron saturates vitreous Tf, creating a pool of NTBI, which could then be taken up by cells and catalyze free radical formation causing oxidative damage to the lens.…”

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confidence: 99%

Vitreous Humor Changes Expression of Iron-Handling Proteins in Lens Epithelial Cells

Goralska

Fleisher

McGahan

2017

Invest. Ophthalmol. Vis. Sci.

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PurposeIn humans, vitrectomy is associated with development of nuclear cataracts. Iron catalyzes free radical formation causing oxidative damage, which is implicated in cataract formation. This study was designed to determine if vitreous humor, which can initiate differentiation of lens epithelial cells, would have an effect on iron-handling proteins.MethodsCultured canine lens epithelial cells were treated with collected canine vitreous humor. Lysates of treated and control cells were separated by SDS-PAGE. Ferritin H- and L-chains, transferrin receptor 1, and aquaporin 0 were immunodetected and quantitated with specific antibodies. Morphologic changes in treated cells were assessed.ResultsTreatment of lens epithelial cells with a 33% (vol/vol) solution of vitreous humor changed the morphology of lens cells and induced expression of aquaporin 0, a marker of fiber cell differentiation that was undetectable in control cells. Treatment did not modify the size of iron-handling proteins but significantly increased content of ferritin from 2.9- to 8.8-fold over control and decreased levels of transferrin receptor by 37% to 59%.ConclusionsVitreous humor may significantly limit iron uptake by transferrin/transferrin receptor pathway, and by increasing ferritin levels could profoundly increase the iron-storage capacity of ferritin in lens cells. Vitreous humor may play a significant protective role against iron-catalyzed oxidative damage of lens epithelial cells and therefore in the formation of cataracts.

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“…kidney, plasma, whole blood, retina, and aqueous humor was completely recovered, recovery from iris, cornea, and lens was less efficient. In a previous study [16], we had found that the poor recovery of gold from several tissues and fluids could be improved by the addition of amino acids (cysteine) and proteins to the samples as matrix modifiers. However, the addition of cysteine as a ma trix modifier in the current investigation did not affect the recovery of added Se.…”

Section: Methodsmentioning

confidence: 99%

Selenium Concentration in Ocular Tissues and Fluids

McGahan

Grimes²

1991

Ophthalmic Res

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A simple, precise method for the analysis of selenium (Se) in ocular fluids and tissues using electrothermal atomic absorption spectroscopy is presented. Se concentrations ranged from 0.23 to 0.41 μg/g wet weight in the cornea, iris, lens, and retina. The Se concentration in aqueous humor was 0.008 μg/ml, thus much lower than that of plasma (0.21 μg/ml). The concentration of protein in aqueous humor is about 1.0% of plasma. Since in plasma, Se is entirely bound to proteins, it is likely that the difference in Se concentration between plasma and aqueous humor reflects the relative distribution of proteins between these fluids.

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A micromethod for the determination of iron and total iron-binding capacity in intraocular fluids and plasma using electrothermal atomic absorption spectroscopy

Cited by 27 publications

References 14 publications

Iron, the retina and the lens: A focused review

Iron, the retina and the lens: A focused review

Vitreous Humor Changes Expression of Iron-Handling Proteins in Lens Epithelial Cells

Selenium Concentration in Ocular Tissues and Fluids

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