March 1994

Ferric Iron Potentiates Cell Depolarization by a Circulating Shock Protein

Author Affiliations

From the Departments of Surgery (Drs Eastridge, Evans, Darlington, and Gann), Biological Chemistry (Dr Evans), and Physiology (Drs Darlington and Gann), the University of Maryland School of Medicine, Baltimore.

Arch Surg. 1994;129(3):245-251. doi:10.1001/archsurg.1994.01420270021005

Objective:  To determine whether or not iron affects the depolarizing activity of a circulating shock protein that appears in plasma after hemorrhage.

Design:  Randomized design.

Setting:  University laboratory.

Animals:  Healthy male Sprague-Dawley rats weighing 300 to 400 g with femoral artery and vein cannulas placed 4 days before hemorrhage.

Intervention:  A 20-mL/kg hemorrhage and plasma collection.

Main Outcome Measures:  Depolarizing activity was measured as the increased fluorescence of an oxonol dye in the presence of Fe3+, Fe2+, or the iron chelator deferoxamine mesylate and was titrated against increasing concentrations of circulating shock protein or iron. Circulating shock protein was derived from plasma and was purified in two steps: stepwise ammonium sulfate precipitation followed by denaturing ion-exchange chromatography and refolding.

Results:  At physiologic concentrations, Fe3+ but not Fe2+ potentiated the depolarizing activity of plasma after ammonium sulfate. Addition of deferoxamine abolished activity. Denaturing chromatography removed nearly all the depolarizing activity; however, Fe3+ restored activity to this fraction. Fe3+ increased total activity and decreased the concentration at which 50% activity was observed.

Conclusion:  These data indicate that physiologic concentrations of Fe3+ may act to modulate the depolarizing activity of circulating shock protein that in turn mediates the intracellular accumulation of salt and water in shock.(Arch Surg. 1994;129:245-251)