EFFECT OF IRON ON SUPEROXIDE METABOLISM - SUPEROXIDE-DISMUTASE INHIBITION AND HYDROXYDOPAMINE ENHANCEMENT

The effect of ferric ion on superoxide dismutase activity as well as on rate of hydroxydopamine oxidation was studied in vitro, since oxygen free radicals (OFR) can cause cellular damage and are mutagenic. Ferric ion inhibits SOD activity in a concentration dependent manner (tested range 0.033-0.066-mu-g iron per a ml of the reaction mixture). The degree of inhibition is directly proportional to reaction time (starting from 3rd minute of the reaction) and to substrate concentration (substrate range 0.38 x 10(-4) M to 0.08 x 10-4 M hydroxydopamine). Ferric ion enhances autoxidation of 6-hydroxydopamine and shortens the time for maximal oxidation reaction from 8 to 4 minutes in the presence of 5-mu-g/ml Fe. The combination of excessive oxygen free radical production and inhibition of their elimination by inhibition of SOD activity may contribute to the mutagenicity and nephrotoxicity of iron which has been detected after iron administration.