Dataset Information

Hydroxyl radical production in body fluids. Roles of metal ions, ascorbate and superoxide.

ABSTRACT: Hydroxyl radical production, detected by ethylene formation from methional, has been investigated in plasma, lymph and synovial fluid. In the presence of added iron--EDTA, addition of either H2O2 or xanthine and xanthine oxidase gave rise to hydroxyl radical formation that in most cases was not superoxide-dependent. The ascorbate already present in the fluid appeared to participate in the reaction. In the absence of added catalyst, the reaction was hardly detectable, the rate being less than 5% of that observed with 1 microM-iron--EDTA added. This implies that the fluids had little if any capacity to catalyse hydroxyl radical production via this mechanism.

SUBMITTER: Winterbourn CC

PROVIDER: S-EPMC1163218 | biostudies-other | 1981 Jul

REPOSITORIES: biostudies-other

ACCESS DATA

Similar Datasets

Project description:A study was made of the interaction of plasma ascorbate and ascorbate free radical (AFR) with exogenously added iron. The quantitative determination of AFR has the advantage that transient increases in ascorbate oxidation can be directly monitored by e.p.r. spectroscopy. An AFR signal was found in the plasma of all donors and was unaffected by superoxide dismutase, catalase and the strong iron chelator deferoxamine. These findings and the rapid decrease in AFR under a nitrogen atmosphere suggest that plasma AFR is probably a result of air auto-oxidation. Iron loading of plasma did not affect the intensity of the AFR signal until the iron concentration approached or exceeded the plasma latent iron-binding capacity. In iron-overloaded plasma, the intensity of the AFR signal increased to about 10 times the normal level before decreasing rapidly to undetectable levels after 15-20 min. Determination of plasma ascorbate showed that the disappearance of AFR was due to a complete loss of the vitamin. When 50 microM-ascorbate was loaded with iron in iso-osmotic phosphate buffer there was an increase in the AFR signal, independent of the iron concentration, which was stable at least for 15 min. Thus the rate of ascorbate loss in the iso-osmotic phosphate buffer was considerably lower than in iron-overloaded plasma. The addition of different iron chelators produced comparable effects on the intensity of the AFR signal in both iron-overloaded plasma and ascorbate solution. These results suggest that the characteristic behaviour of plasma AFR after iron loading is due to its specific iron-binding capacity and to plasma ferroxidase activity. The ferroxidase activity of plasma is important to promote the transfer of Fe2+ into transferrin without a transient ascorbate oxidation. Spin-trapping studies with 5,5-dimethyl-1-pyrroline N-oxide and N-t-butyl-alpha-phenylnitrone revealed that iron-overloaded plasma was unable to produce spin-trap adducts even in the presence of 50-300 microM-hydrogen peroxide or 100 microM-azide. Evidence of OH. radical formation was obtained only after the addition of EDTA. Therefore, iron-overloaded plasma itself does not produce a Fenton reaction and, if ascorbate does indeed have a free-radical-mediated pro-oxidant role, it is not detectable in plasma by spin-trapping experiments.

Dataset Information

Hydroxyl radical production in body fluids. Roles of metal ions, ascorbate and superoxide.

Similar Datasets

OmicsDI is part of the ELIXIR infrastructure

Tweets