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The effect of Al on superoxide dismutase (SOD) and on other antioxygenic enzymes: horseradish peroxidase, catalase, and glutathione peroxidase, has been investigated in vitro. In the case of SOD, the effect of metal chelators (EDTA and deferoxamine) and a possible synergistic effect with iron salts have also been tested using the pyrogallol assay. There was no significant inhibitory effect of Al on the activity of any of the above-mentioned enzymes. Noticeable increases in SOD activity were observed when metal chelators were added to the medium, but not when high concentrations of Al were also present, in the case of deferoxamine (DFO). The former fact seems to be a consequence of the chelation of transition metal ions that catalyse pyrogallol autoxidation by a mechanism not inhibitable by SOD, interfering in its action, which may account for part of the DFO antioxidant effect observed in vivo. The latter phenomenon could be due to a saturation of the chelating capacity of DFO by an excess of Al present in the medium, which would bring the system back to the interfering conditions explained above. It can be concluded that Al, either in the presence or in the absence of iron salts, does not inhibit SOD activity in vitro. Moreover, no significant binding of Al to SOD was demonstrated, and the amounts of its metal constituents, Cu and Zn, were not affected by preincubation of the enzyme with Al. The effect of the different compounds tested on the rate of autoxidation of the indicating scavenger, pyrogallol, and a hypothesis of their role in the oxidation process, are also discussed.

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Authors: SABBIONI E, JRC Ispra (IT);SERRA M A, JRC Ispra (IT);BARASSI V, JRC Ispra (IT);CANAVESE C, University of Turin, San Giovanni-Molinette Hospital, Department of Nephrology (IT)
Bibliographic Reference: Article: Biological Trace Element Research, Vol. 31 (1991) pp. 79-96
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