Chronically inflamed tissues contain significant concentrations of oxy
gen radicals, possibly generated by transition metal species such as F
e(II) and Cu(I). In addition, the pH of such tissues may well be lower
than that of normal counterpart tissues. In this communication, the e
ffect of variation of pH on the antioxidant activity of caeruloplasmin
(a copper-containing acute-phase protein possessing important ferroxi
dase and other antioxidant activities) and of heparin are reported. He
parin, unlike caeruloplasmin, retains antioxidant activity at low pH.
Heparins possess a variety of metal cation-binding chemical groups all
owing them to bind damaging Cu(I) and Fe(II) ions and consequently pre
vent their redox involvement in oxygen radical-generating Fenton react
ions. In conclusion, heparins may function as endogenous antioxidants
and sequestration and/or oxidation by them, of ions such as Fe(II), ma
y contribute to their effectiveness.