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Electron Paramagnetic Resonance Analysis of Transferrin-Bound Iron in Animal Models of Blunt Trauma

Gorbunov, Nikolai V. PhD; Nath, Jayasree PhD; Parker, Joseph M. MD; Zaucha, Gary M. DVM

The Journal of Trauma: Injury, Infection, and Critical Care: March 2003 - Volume 54 - Issue 3 - p 574-583
doi: 10.1097/01.TA.0000043922.40376.38
ORIGINAL ARTICLES
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Background  Blood iron sequestration is known to be implicated in the systemic acute-phase response to trauma injury. The objective of the present research was to assess the effect of iron sequestration in animal models of blunt trauma by means of electron paramagnetic resonance spectroscopy of iron in complex with transferrin, a main iron-transporting protein in blood, and to correlate this effect with the extent of induced injury.

Methods  Two animal models of blunt trauma were explored in the present study. Blunt trauma in the rat model was produced by exposure of 14 animals to blast overpressure (BOP) (at peak BOP of either 86 ± 5 kPa or 112 ± 2 kPa) generated in a shock tube. Blunt trauma in the porcine model was produced by impact of high-speed projectiles made from a rubber-tipped, plastic composite weighing 28.64 ± 0.12 g (mean ± SEM, n = 8) with a length of ∼6 cm and a diameter of ∼4 cm. The projectiles were propelled by compressed helium onto eight animals at a velocity of 101.8 ± 3.8 m/s (mean ± SEM, n = 8) at the point of impact. Each experiment was accompanied by a pathology assessment using an injury scoring system developed for blunt trauma injuries to derive a severity score for whole-body involvement. Amounts of transferrin-bound iron (TRF-[Fe3+]) in whole blood and blood plasma samples were measured using quantitative electron paramagnetic resonance spectroscopy. The observed alterations in the amounts of blood TRF-[Fe3+] were correlated with estimated injury score ratios in each animal.

Results  Blunt trauma produced by either BOP exposure of rats or projectile impacts in pigs was accompanied by TRF-[Fe3+] sequestration observed in both blood and blood plasma. The amount of TRF-[Fe3+] in blood was shown to have inverse correlation with the extent of injury (Pearson r = −0.90 in the rat model and r = −0.93 in the porcine model) estimated by injury score ratios and was not dependent on location of the injury (lung, liver, spleen, or jejunum).

Conclusion  The presented data suggest that assessment of TRF-[Fe3+] in blunt trauma can provide a good deal of information on severity of injury. The response of TRF-[Fe3+] can be considered as a potential surrogate marker of the systemic alterations in blunt trauma and, therefore, warrants further investigation in a human pilot study.

From the Department of Respiratory Research, Division of Military Casualty Research (N.V.G., J.N., J.M.P.), and Department of Comparative Pathology, Division of Pathology (G.M.Z.), Walter Reed Army Institute of Research, Silver Spring, Maryland.

Submitted for publication October 8, 2001.

Accepted for publication October 15, 2002.

Supported by a Senior Research Associateship Award from the National Research Council (to N.V. Gorbunov).

The views, opinions, and/or findings contained herein are those of the authors and should not be construed as an official Department of the Army position, policy, or decision unless so designated by other documentation.

Address for reprints: Nikolai V. Gorbunov, PhD, Department of Respiratory Research/MCR, Walter Reed Army Institute of Research, 503 Robert Grant Avenue, Room 1A14, Silver Spring, MD 20910; email: nikolai.gorbounov@na.amedd.army.mil.

© 2003 Lippincott Williams & Wilkins, Inc.