Ferric iron potentiates cell depolarization by a circulating shock protein.
OBJECTIVE
To determine whether or nor iron affects the depolarizing activity of a circulating shock protein that appears in plasma after hemorrhage.


METHODS
Randomized design.


METHODS
University laboratory.


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


METHODS
A 20-mL/kg hemorrhage and plasma collection.


METHODS
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.


CONCLUSIONS
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.
Eastridge
B J
BJ
Department of Surgery, University of Maryland School of Medicine, Baltimore.
Evans
J A
JA
Darlington
D N
DN
Gann
D S
DS
D000818:Animals; D003676:Deferoxamine / Q000494:pharmacology; D004305:Dose-Response Relationship, Drug; D004594:Electrophysiology; D004910:Erythrocyte Membrane / Q000187:drug effects*; D005290:Ferric Compounds / Q000494:pharmacology*; D005296:Ferrous Compounds / Q000494:pharmacology*; D005420:Flavoproteins / Q000494:pharmacology; D006360:Heat-Shock Proteins / Q000097:blood / Q000187:drug effects* / Q000502:physiology; D006470:Hemorrhage / Q000097:blood*; D008297:Male; D011732:Pyridoxal Phosphate / Q000494:pharmacology; D011897:Random Allocation; D051381:Rats; D017207:Rats, Sprague-Dawley
D005290:Ferric Compounds; D005296:Ferrous Compounds; D005420:Flavoproteins; D006360:Heat-Shock Proteins; D011732:Pyridoxal Phosphate; D003676:Deferoxamine